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 side rails. Fixed aluminum lock allows push up height adjustment. Shoe pivots to allow the shoe pad full ground contact for slip-resistance. U.L. Listed. Meet ANSI Code. Dimensions: Side rails 2-1/2" wide; Flange 3/4" wide; Rungs 1-1/4" wide; Base width 15-3/4" outside rails. Length of extension ladders when not extended is half the total length of the sections.