The uniform distribution of the groove-shaped slots or notches 21, 22 along the foundation strips 12, 13 of the tread 1 subdivide the outer edges 24a, 24b into a plurality of substantially equal wide rim foundations 23 which effect a type of claw action to increase the traction of the tread 1 travelling along a flat surface such as, for example, a floor of a gymnasium or other playing surface, by