BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a schematic view of a structure of the present invention;
FIG. 2 is an enlarged view of Portion 2 depicted in FIG. 1;
FIG. 3 is a schematic view of a structure of a preferred embodiment of the present invention; and
FIG. 4 is a schematic view of a structure of another preferred embodiment of the present invention.