Tread configuration on folding case

FIG. 1 is a perspective view of the tread configuration in folded condition for use on a front side and an end portion of a folding case shown in broken lines;

FIG. 2 is a perspective view of the tread design for use on a rear side of the FIG. 1 case;

FIG. 3 is a plan view of the FIG. 1 and FIG. 2 tread configuration in unfolded condition for use on front and rear sides, and at the end, of the FIG. 1 case shown in broken lines; and,

FIG. 4 is a plan view like FIG. 3, showing a modified tread configuration with arcuate edges, for use on front and rear sides, and at the end, of a modified case shown in broken lines.