A roll formed step rail for a vehicle comprises an elongated rail body having two opposing edges which define a longitudinal channel. The channel receives a pinch clamp which is wider than the channel and has a fastening hole and an alignment means. The rail body is lowered onto the mounting surface of a mounting bracket adapted for rigid connection to a vehicle. The mounting surface defines another fastening hole and another portion of the alignment means. A fastener draws the pinch clamp and the mounting surface toward opposite sides of the opposing edges of the rail body. Because the pinch clamp spans the width of the channel and is aligned properly relative to the mounting surface, the rail body is secured between the clamp and the mounting surface by the tightened fastener.