Climbing nut

Information

  • Patent Grant
  • 6273379
  • Patent Number
    6,273,379
  • Date Filed
    Tuesday, May 9, 2000
    24 years ago
  • Date Issued
    Tuesday, August 14, 2001
    23 years ago
Abstract
A climbing nut is generally trapezoidal and has planar upper and lower faces and paired adjacent faces that are convex and concave, respectively. Opposed faces of the nut are therefore convex and concave, respectively. The convex faces have lateral longitudinally extending leg segments that assist in triangulation and strengthen the nut. The geometry of the faces allows for greater placement options. The nut alternately has one or more asymmetric curved faces. The nut is milled from stock extrusion material.
Description




FIELD OF THE INVENTION




This invention relates passive climbing protection devices, and more particularly, to a climbing nut having curved faces.




BACKGROUND OF THE INVENTION




Climbers use various types of active and passive devices as protection against falls. Active devices generally include some kind of mechanical parts that assist in anchoring the protection on the rock wall. A cam is an example of an active device. Passive devices, on the other hand, do not include mechanical parts for attachment to the rock, and instead rely upon friction and gravitational forces to achieve anchoring. One type of passive protection is a climbing nut, which may also be referred to as a chock.




Climbing nuts are made in many different shapes, but many are generally formed as trapezoidal wedges. During a climb, nuts of appropriate size are wedged into cracks in the rock and a climbing rope is connected indirectly to the nut through various slings and like devices. To ensure proper placement of the nut (i.e., the “protection”) it is important that the protection is not moved once it is set in the crack, such as being rocked back and forth in the crack as the rope moves through the attached carabiner. Therefore, each nut includes a loop or sling of cable attached to it. A carabiner is typically attached to the cable and a loop of webbing is attached to the carabiner. Another carabiner is then connected to the opposite end of the webbing and the rope is passed through the second carabiner. This system allows the rope to move freely through the carabiners without unduly moving the nut and risking its coming loose.




The wedge shape allows the nut to be pulled upwardly to release it from its engagement with the rock. As a climber progresses up a climb the nuts may be pulled upwardly and out of the crack when they are no longer needed. The nut may then be reused on the next pitch. On the other hand, if a climber falls the wedge shape of the nut provides a secure anchor, as the climbing rope becomes taut during the fall, thereby arresting the climber's fall.




Proper placement of nuts is obviously very important since improper placement can lead to failure of the protection when it is most needed. One important aspect of the placement is the attainment of triangulation between the nut and the rock. In other words, for proper holding strength it is important that there are at least three points of contact between the nut and the rock. When the nut is properly seated in a crack with proper triangulation the nut provides adequate anchoring strength. However, cracks in rocks are rarely regular in geometric shape. They are, instead, typically curved and irregularly shaped. Moreover, many cracks flare either inwardly or outwardly. With such irregular rock formations it can be difficult in some cases to visually verify that nut placement has achieved correct triangulation.




With standard nuts that are trapezoidal in shape with opposed straight tapered faces the nuts tended to have only two points of contact with the rock. Two points of contact is insufficient for a variety of reasons, including insufficient holding strength, and also the tendency of the nut to pivot back and forth in the rock about the two contact points as the rope moves through the attached carabiners. This pivoting can lead to loosening of the protection and in extreme cases can lead to the nut coming out of the crack. However, with nuts having this geometry visual verification of placement in a crack is relatively easily accomplished.




Various shapes of nuts have been designed over the years to improve placement options and to improve triangulation. As noted, one standard shape is a straight-sided wedge with a constant taper angle. Nuts with this shape are ubiquitous and may be beneficially used in many situations. But given the irregularities in the shapes of cracks, such nuts have limited placement options. Further, while visual verification is easy, unless a crack is relatively straight-sided and the contours of the crack match the geometry of the nut, it can be very difficult to attain proper triangulation. As would be expected, it is a relatively rare occasion when the geometry of a crack conforms to the geometry of a nut. This can lead to the nut pivoting or rocking back and forth in the crack.




Various nut designs have been implemented to increase holding ability and the ability to verify correct placement. One such design shown in U.S. Pat. No.4,083,521 comprises a “trefoil” nut having three equiangular arms radially extending from a center point. The body of the nut is generally trapezoidal as viewed in a side elevation. The patent notes that the device allows for easy placement and retrieval. However, while this nut does improve the ability to achieve triangulation, it presents limited placement options given the equiangular and equal length radial arms. In addition, visual verification of proper triangulation is difficult.




Another improved nut design is disclosed in U.S. Pat. No. 4,422,607. The nut described in that patent is generally wedge shaped, but two opposite faces of the nut are respectively concave and convex, with the cylindrical axis of the concave and convex curvature extending transverse to the vertical axis through the nut. The nut described in this patent is an improvement over wedge shaped nuts having straight tapering sides since with it triangulation is more easily accomplished. However, with this nut it can be difficult to visually ensure that the nut is properly placed. More particularly, in some placement situations it can be difficult to visually determine if the nut of the '607 patent will be prone to rock out of the placement if a sudden load is placed on the nut, as in a fall. This is because the axis of the curved faces extends across the nut, transverse to the axis along which a load is placed during a fall. Thus, with this geometry it is difficult to verify proper placement in many types of cracks. As noted, many cracks exhibit either inward or outward flaring. Given the geometry of the nut of the '607 patent, placement of the nut in flared cracks is difficult and verification of proper placement is likewise difficult.




Other nuts having a modified wedge shaped have also been developed. For example, in one prior art trapezoidal shaped wedge nut, both opposed “wide” faces of the nut are concave with the cylindrical axis of the concave sections extending generally parallel to the long axis through the nut, and thus parallel to the direction that a load is exerted in a fall. The concave sections define longitudinal rails along the outer sides of the faces. The side faces are planar. In one modified embodiment of this kind of a nut the wide faces have a radius of curvature rather than having a straight sided taper and the top and bottom surfaces are not co-planar. With these nuts, triangulation, while difficult in some crack contours, is generally improved. However, visual inspection tends to be difficult.




There is a need therefore for a climbing nut that improves on prior nuts, provides improved protection and holding strength, provides for more placement options in cracks having varying geometry, and which allows for quick and accurate visual verification of placement.




Prior art nuts such as those described above are typically manufactured by casting, or by cutting extruded stock into desired lengths. For example, the nut described in the '521 patent described above is said to be manufactured from extruded metal or plastic stock. Nuts such as those shown in the '607 patent may also be cut from extruded stock. An alternative method of manufacturing nuts is by well-known forging or casting techniques. With nuts that have variable geometry and multifaceted faces, it is not possible to make suitable extrusion stock material. Moreover, even if stock material could be made it is not always possible or economical to cut the stock into lengths with the cut faces having the proper geometry. In such cases casting is an acceptable alternative method of making the nut.




Both the extrusion and casting methods work well, but both have limitations. For instance, with the extrusion method there are severe limits on the angular geometric face shapes that can be produced. And if the lateral cut sides of the nut are to be any shape other than planar, extrusion cutting is essentially impossible. Cast nuts may be manufactured in virtually any shape. However, casting is a time consuming and sometimes difficult process that requires special equipment. Molds must be made for each specific geometric shape, and quality control over the alloys used must be closely watched.




There is a need therefore for alternative methods of manufacturing nuts having multifaceted faces.




SUMMARY OF THE INVENTION




The advantages of the present invention are achieved in a first preferred embodiment of a wedge shaped climbing nut having side faces that taper from an upper face to a lower face. Both sets of opposed side faces are concave and convex, respectively, and the axis of the concave and convex curved faces extends along the longitudinal axis of the nut along which a load is placed during a fall. Thus, two convex faces are adjacent one another and two concave faces are adjacent one another. The nut of the present invention allows for more placement options in a wider variety of crack formations and allows for better triangulation and visual verification.




As yet another embodiment of the nut of the present invention, one or both of the adjacent convex faces may have an asymmetric radius of curvature. This allows for further placement options.




The nut of the present invention is manufactured by milling the nut from an extruded blank of rectangular material. The milling is accomplished with a specific combination of milling steps, which are carried out according to computer numeric controlled (CNC) processes. By milling the nut from extruded blank stock the alloy consistency of the nut is assured and there is greater flexibility in the geometric configurations for the faces of the nut.











BRIEF DESCRIPTION OF THE DRAWINGS




The invention will be better understood and its numerous objects and advantages will be apparent by reference to the following detailed description of the invention when taken in conjunction with the following drawings.





FIG. 1

a perspective view of a climbing nut according to a preferred embodiment, illustrating the respective adjacent convex side faces of the nut.





FIG. 2

is a perspective view of the nut shown in

FIG. 1

illustrating the respective concave side faces.





FIG. 3

is an elevational view of the convex side face of the nut of FIG.


1


.





FIG. 4

is an elevational view of the concave side face of the nut of FIG.


1


.





FIG. 5

is a top plan view of the concave front face of the nut of FIG.


1


.





FIG. 6

is a bottom plan view of the convex rear face of the nut of FIG.


1


.





FIG. 7

is a bottom plan view of the nut of FIG.


1


.





FIG. 8

is a top plan view of the nut of FIG.


1


.





FIG. 9

is a plan view of a nut according to this invention including a cable sling.





FIG. 10

is a schematic side view showing one placement of a nut according to the present invention in a tapered crack.





FIG. 11

is schematic top view of a nut of the present invention placed in a flared crack.





FIG. 12

a schematic top view similar to the view of

FIG. 11

showing an alternate placement the nut in a flared crack.





FIG. 13

is a perspective view of an alternate embodiment of a nut according to the present invention, in which one convex face is asymmetrically curved.





FIG. 14

is a perspective view of an ingot of extruded blank metal from which the nut present invention is milled.





FIG. 15

is a perspective view of the ingot of

FIG. 14

with several nuts shown in progressive stages of the milling process.











DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS




Referring to

FIG. 1

, a nut


10


according to the present invention may be seen as having a generally trapezoidal wedge shape with six surfaces or faces. The following naming convention is used throughout for reference purposes. The two wider faces of nut


10


are convex front face


12


and opposite concave rear face


14


. The two relatively narrower lateral side faces are convex side face


16


and opposite concave side face


18


. The two opposed end faces are lower end face


20


and upper end face


22


. Opposed end faces


20


and


22


are coplanar, and upper end face


22


is larger than lower end face


24


. A pair of bores


24


and


26


extend side by side completely through nut


10


parallel to the longitudinal axis through the nut and, as shown in

FIG. 9

, are designed to receive cable


28


(FIG.


9


). Cable


28


thus extends upwardly through bore


24


and is then looped over and runs through bore


26


. The two ends of the cable are then connected, for instance with a swaged fitting


30


that defines a looped end


32


. Dual bores with a looped cable provide the strongest attachment for the cable and are thus preferred, though alternates (including a single bore) are available depending upon the size of the nut.




The nut of the present invention may be manufactured in various sizes to be used in cracks of various sizes. With the larger nuts a trough may be countersunk or otherwise formed in upper end face


22


between bores


24


and


26


to form a seat for the cable. The seat provides a smoother curvature for the cable and therefore reduces wear on the cable.




Although not shown, in use, a carabiner is connected to looped end


32


of cable


28


(FIG.


9


), and a looped section of webbing is connected to the carabiner. A second carabiner is then connected to the opposite end of the webbing, and the climbing rope is run through the second carabiner. It will be appreciated that the nut is designed to be wedged into place such that a load on the nut is exerted in the vertical direction as the nut is placed in a crack. Stated otherwise, the load on the nut when it is under load is preferably exerted in the direction generally parallel to the longitudinal axis through the nut, which as noted above, is parallel to the direction of bores


24


,


26


.




With reference to

FIGS. 3 through 6

it may be seen that the faces


12


,


14


,


16


and


18


taper angularly from upper end face


22


converging toward lower end face


20


. The angle at which the opposed faces taper from face


22


to face


20


is the same for each opposed face, and the taper is thus equiangular. Stated another way, there is a constant taper angle in each of the opposed faces moving from upper end face


22


to lower end face


20


. That is, the faces define straight sided and planar tapered surfaces when in side elevation as in

FIGS. 3 through 6

.




The two adjacent convex faces, convex front face


12


and the adjacent convex side face


16


, are both radially symmetrically curved about a centerline extending along the faces to define the convex surfaces (see FIGS.


7


and


8


). The two adjacent concave faces


14


and


18


similarly have radially symmetrically curved concave channels formed therein to define the concave faces.




With reference to

FIG. 2

, a radially curved concave channel


32


extends along the length of concave rear face


14


from lower face


20


to upper face


22


. Channel


32


extends laterally from the longitudinal centerline of face


14


outwardly toward the lateral side edges of the face. However, the concave section does not extend completely to the lateral side edges of the face, and instead terminates inwardly of both lateral side edges to define planar leg sections


34


and


36


that extend longitudinally along the lateral edges of the face along the length of the nut. The width of the concave channel


32


increases slightly in the direction from lower face


20


toward upper face


22


(see FIGS.


5


and


7


), and the width of each of the planar leg sections


34


and


36


accordingly increases slightly in the same direction length of nut


10


. Similarly, a radially curved concave channel


38


extends along the length of concave side face


18


from lower face


20


to upper face


22


. Channel


38


extends laterally from the longitudinal centerline of face


18


outwardly toward the sides of the face. However, the concave section does not extend completely to the side edges, and instead terminates inwardly of both side edges to define planar leg sections


40


and


42


that extend longitudinally along the length of the nut. The width of the concave channel


38


increases slightly in the direction from lower face


20


toward upper face


22


(see FIGS.


4


and


7


), and the width of planar leg sections


40


and


42


accordingly increases slightly in the same direction along the entire length of nut


10


.




As may be seen in the figures, the curvature of the concave and convex faces extends along the axis through the nut defined by bores


24


and


24


, as opposed to the curvature of these faces extending transverse to such axis. Thus, a cylindrical axis defined by the respective concave and convex curved surfaces extends in a direction generally the same as the axis through the nut defined by bores


24


and


26


. Since the opposed faces of the nut converge from upper face


22


toward lower face


20


, the cylindrical axes just mentioned actually either converge toward or diverge from the axis defined by the bores at an angle defined by the angle of the tapered sides. Nonetheless, it will be appreciated that these cylindrical axes of the concave and convex surfaces extend generally parallel to the axis defined by the bores. This orientation may be contrasted with some prior art nuts such as the nut described in U.S. Pat. No. 4,422,607 in which the cylindrical axes defined by the concave and convex surfaces is generally transverse or orthogonal to the axis of the cable-receiving bores.





FIGS. 10 through 12

show various alternate placement positions for the nut of the present invention. In

FIG. 10

the crack in the rock exhibits a downward taper. The nut


10


is placed in the crack such that it makes at least three points of contact with the rock at its convex face


12


and on its concave face


14


on legs


36


and


34


(leg


34


is obscured in the view of FIG.


10


). In the event of a fall a sudden and significant load is placed on the nut, and as described above, the load is exerted in the vertical direction, or the direction parallel to the longitudinal axis through the nut. Because legs


34


and


36


define planar sections the load exerted on the nut is spread over a relatively larger area than if the concave channel


32


extended completely to the lateral side edges of face


14


. This design thus increases the strength of the nut. The combination of opposed concave and convex faces allows the nut to triangulate regardless of irregularities in the rock formation geometry. Nut


10


thus combines the visual verification advantages of a traditional straight sided tapered wedge with the improved triangulation of curved faces.




Two rock cracks having different flared geometry are illustrated in

FIGS. 11 and 12

. In

FIG. 11

nut


10


is wedged into the crack such that triangulation is achieved on face


12


and on legs


34


and


36


, respectively. It will be appreciated that with the cylindrical axis of curvature of the concave and convex faces extending generally along the longitudinal axis of the nut, the relative angle of flaring in the crack will not effect the ability of the nut to triangulate properly, although the actual position of the contact between the rock and the nut will vary according to the contours of the crack. In

FIG. 12

a crack having similar flaring geometry is shown, except nut


10


is wedged into the crack with the triangulation or contact points on face


16


, and legs


40


and


42


.

FIG. 12

illustrates that by manufacturing the nut with the two pairs of opposed concave and convex faces, a nut that has a width dimension that is greater that its depth dimension allows the same nut to be used in cracks of different sizes.




An alternate embodiment of nut


10


is shown in FIG.


13


. Nut


10


of

FIG. 13

has the same basic configuration as the nut shown in

FIGS. 1 through 12

, except that the curvature of convex front face


44


is asymmetric about a longitudinal centerline extending along the face. The asymmetrically curved face provides for different placement options in cracks having different contours. Moreover, convex side face


16


may likewise be formed with an asymmetric curvature and either one or both of the concave curves on faces


14


and


18


could be asymmetrically curved.




Method of Manufacture





FIG. 14

shows an ingot


46


of extruded metal from which a plurality of nuts


10


will be milled. The alloy composition of ingot


46


is selected according to design preferences and strength requirements, and is closely controlled to meet desired specifications. The size dimensions of ingot


46


depend upon the size of the nuts that will be milled from it, but as can be seen, the ingot is rectangular in sectional shape.




A milling machine utilizing computer numeric control mills a plurality of nuts from ingot


46


. Depending upon the type of milling machine that is used, nuts may be milled one at a time or several at a time. Tapered end mill bits are selected for cutting the pieces according to the size and dimensions of the cuts that are being made. For explanatory purposes the milling process will be described with reference to milling a single nut. However, it will be appreciated that some kinds of CNC milling machines allow for simultaneous milling of several pieces.




The CNC machine is under the control of a computer processor, which is informed of appropriate coordinates for making the cuts. An ingot


46


is placed in the CNC mill vise (not shown) and the milling process begins with appropriate tapered end mill bits being loaded into the cutting head. With reference to

FIG. 15

, the cutting process begins by cutting ingot


46


to mill nut


48


. The mill first cuts ingot


46


to define opposed convex front face


12


and concave rear face


14


, and opposed convex side face


16


and concave side face


18


. Lower end face


20


of nut


48


is defined by the upper surface of ingot


46


. Depending upon the types of cuts that are being made, appropriate tooling changes may be necessary during the milling process, for example, interchanging mill bits. Selection of appropriate tooling is within the ordinary ability of those skilled in the art. Bores


24


and


26


are then drilled through nut


48


.




At this point the portion of nut


48


that will become upper end face


22


is still an integral part of ingot


46


. In

FIG. 15

, nuts


48


,


50


and


52


are all shown with the portion of the nuts that will be the upper end faces still part of the ingot. When a plurality of nuts have been cut from ingot


46


as described, a side cut saw blade cuts longitudinally along ingot


46


at the “base” of the nuts as shown in

FIG. 15

with respect to nuts


54


and


56


to define upper end faces


22


. The side cut saw blade does not cut the nuts completely away from the remaining portions of ingot


46


. Instead, a flange


58


remains and holds the nuts onto the ingot. With all of the nuts on an ingot cut in this manner, the ingot may be removed from the mill vise and the individual nuts snapped off the ingot by breaking flange


58


. This typically may be done by hand. The individual nuts are then deburred to remove and surface blemishes or burrs, and a cable


28


is connected to the nut in the manner described above.




By milling the nuts from an ingot with a CNC milling machine the manufacturing process is essentially a one-step process. Controlling the cutting process closely controls the quality of the nut, and the consistency of the alloy is assured. Moreover, for the reasons described above, with nuts having geometry such as nut


10


of the present invention, the only alternate method of manufacturing is casting the nut. The present method of manufacturing is a marked improvement over casting in terms of quality and efficiency.




While the present invention has been described in terms of a preferred embodiment, it will be appreciated by one of ordinary skill that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims.



Claims
  • 1. A climbing nut comprising:a body having at least one bore extending therethrough between an upper face and an opposed lower face, said bore defining a longitudinal axis through the body, a first pair of opposed side faces and a second pair of opposed side faces, one face of each of said pairs defining a concave surface and the opposite face of each of said pairs defining a convex surface, said concave and convex surfaces defining longitudinal axes that extend in the same general direction as the longitudinal axis through the body; and a looped cable extending through said at least one bore.
  • 2. The climbing nut of claim 1 wherein said upper and opposed lower faces are coplanar.
  • 3. The climbing nut of claim 2 wherein said upper face is larger than said lower face to define a body that is generally trapezoidal.
  • 4. The climbing nut of claim 3 wherein said first opposed side faces converge from said upper face to said lower face to define tapered opposed faces.
  • 5. The climbing nut of claim 4 wherein said first opposed side faces taper equiangularly from said upper face to said lower face.
  • 6. The climbing nut of claim 3 wherein said second opposed side faces converge from said upper face to said lower face to define tapered opposed faces.
  • 7. The climbing nut of claim 6 wherein said second opposed side faces taper equiangularly from said upper face to said lower face.
  • 8. The climbing nut of claim 1 wherein in side elevation said body defines a trapezoid having straight sides.
  • 9. The climbing nut of claim 1 wherein a cylindrical axis of said concave and convex surfaces is generally parallel to the axis through said nut.
  • 10. The climbing nut of claim 1 wherein said concave surfaces have lateral side edges and at least one of said concave surfaces further comprises a concave section extending only partially across said face to define opposed leg sections extending along the lateral edges of said face.
  • 11. The climbing nut of claim 10 wherein each of said concave surfaces comprises a concave section extending only partially across said faces to define opposed leg sections on adjacent faces, each of said opposed leg sections extending along the lateral edge of said faces.
  • 12. The climbing nut of claim 1 wherein at least one of the convex surfaces defines a surface that is symmetrically curved about a longitudinal centerline extending along said surface.
  • 13. The climbing nut of claim 1 wherein at least one of the convex surfaces defines a surface that is asymmetrically curved about a longitudinal centerline extending along said surface.
  • 14. A climbing nut comprising:a body comprising: (a) an upper surface and an opposed lower surface that is smaller than said upper surface; (b) a pair of bores extending between said upper and lower surfaces and defining an axis through said body; (c) a first pair of opposed side faces, one face of said pair convex and the other face of said pair concave, each of said convex and concave faces defining a longitudinal axis, wherein said longitudinal axes are not transverse to said axis through said body and are generally parallel to said axis through said body; (d) a second pair of opposed side faces, one face of said pair convex and the other face of said pair concave; wherein in side elevation said body defines a trapezoid; and a looped cable extending through said bores.
  • 15. The climbing nut of claim 14 wherein said bores are parallel and define an axis through said body.
  • 16. The climbing nut of claim 14 wherein at least one of the convex surfaces defines a surface that is symmetrically curved about a longitudinal centerline extending along said surface.
  • 17. The climbing nut of claim 14 wherein at least one of the convex surfaces defines a surface that is asymmetrically curved about a longitudinal centerline extending along said surface.
  • 18. The climbing nut of claim 14 wherein each of said concave faces defines opposed lateral side edges, and each of said concave faces further comprises planar legs extending along said lateral side edges.
  • 19. A climbing nut comprising:a body having at least one bore extending therethrough between an upper face and an opposed lower face, said bore defining an axis through the body, a first pair of opposed side faces and a second pair of opposed side faces that taper equiangularly from said upper face to said lower face, one face of each of said pairs defining a concave surface and the opposite face of each of said pairs defining a convex surface, said concave and convex surfaces defining cylindrical axes that extend in the same general direction as the axis through the body; and a looped cable extending through said at least one bore.
  • 20. A climbing nut comprising:a body having at least one bore extending therethrough between an upper face and an opposed lower face, said bore defining a longitudinal axis through the body, a first pair of opposed side faces and a second pair of opposed side faces, one face of each of said pairs defining a concave surface and the opposite face of each of said pairs defining a convex surface, said concave and convex surfaces defining cylindrical axes that extend in the same general direction as the longitudinal axis through the body; a looped cable extending through said at least one bore, and wherein a cylindrical axis of said concave and convex surfaces is generally parallel t the axis through said nut.
  • 21. A climbing nut comprising:a body having at least one bore extending therethrough between an upper face and an opposed lower face, said bore defining an axis through the body, a first pair of opposed side faces that taper equiangularly from said upper face to said lower face, and a second pair of opposed side faces that converge from said upper face to said lower face to define tapered opposed faces, one face of each of said pairs defining a concave surface and the opposite face of each of said pairs defining a convex surface, said concave and convex surfaces defining cylindrical axes that extend in the same general direction as the axis through the body; and a looped cable extending through said at least one bore.
US Referenced Citations (4)
Number Name Date Kind
4083521 Greiner Apr 1978
4422607 Vallance Dec 1983
6070842 Sandahl Jun 2000
6119993 Youngblood et al. Sep 2000
Foreign Referenced Citations (3)
Number Date Country
3526402-A1 Feb 1987 DE
106645-A1 Apr 1984 EP
2553668-A1 Apr 1985 FR
Non-Patent Literature Citations (2)
Entry
Photographs of climbing nut 1, front and rear sides labelled A, B, respectively, circa 1995.
Photographs of climbing nut 2, front and rear sides labelled A, B, respectively, circa 1995.