Twist-Proof due to the Alflo rung joints. Mar-resistant molded end caps and rail closures. Traction-Tred deeply serrated flat steps. Easy to grip modified I-beam siderails. Smoothly operating extruded aluminum double rung locks. Shoe pivots to allow the shoe pad full ground contact for slip-resistance. Equipped with rope and smooth operating pulley except for No. D1116-2. U.L. Listed. Meets ANSI Code and OSHA requirements. Dimensions: Siderails 2-3/4 in wide (16 ft and 20 ft ) 3 in wide (24 ft to 28 ft ); Flange 15/16 in wide; Rungs 1- 1/2 in wide; Base width 16 in outside rails. Length of extension ladders when not extended is half the total length of the sections.