the riser the pair of male hinge members 302 being spaced apart to form an aperture or recess 7 rr that is complementary to and receives the at least one male hinge member 300 each of the male hinge members 300 302 comprises a center arcuate member 300 c 302 c having an outside wall 300 w 302 w that extends continuously from the upper step surface ss of the step and the outside surface os of the riser at least about 180 degrees angle b around the rear 50 e and front 60 e edges of the step 50 and the riser 60 respectively each of the male hinge members 300 302 further comprises a pair of lateral arcuate fingers 300 f 302 f disposed on opposing lateral sides of the center arcuate member 300 c 302 c the lateral arcuate fingers 300 f 302 f having an outside surface 300 fw 302 fw that extends continuously from the upper step surface ss of the step 50 and from the outside surface os of the riser about 90 degrees angle c around the rear 50 e and front edges 60 e of the step and the riser the male hinge members 300 302 each have a longitudinal aperture 300 ap 302 ap with a common axis apx for receiving a pin or rod 72 p that extends through the longitudinal aperture 300 ap.