FIG. 1 is an isometric front, top and first side view of the knife sheath showing our new design; FIG. 2 is an orthographic first side view thereof; FIG. 3 is an orthographic second side view thereof; FIG. 4 is a top plan view thereof; FIG. 5 is a bottom plan view thereof; FIG. 6 is an orthographic front view thereof; FIG. 7 is an orthographic rear view thereof; and, FIG. 8 is an isometric rear, top and second side view thereof.