Four solid 1/4-Inch rivets attach top to front rails on each side. 5/16-Inch shoulder bolt and lock nut on top hinge, massive 3/16-Inch thick side plates. Rear horizontals are spaced 12-Inch apart with knee-bracing mounted on full U-channel rear rails. Heavy duty black slip-resistant feet. Traction-Treed deeply serrated steps provide extra safety.