Super heavy duty industrial design. Our aluminum folding stairway features large 5” channel stringers with 5-3/16” deep x 21-1/4” wide serrated aluminum treads. A 1/8” thick aluminum door is mounted to a steel piano hinge for maximum strength while opening and closing. The 5” deep stairway frame is constructed from 1/8” steel, formed channel. A steel bar handrail, on both sides adds safety while climbing. All ladders are 21-1/4" wide.