Abstract: An aluminum side rail for use in fabricating the side walls of a truck body. The rail has a hollow, rectangular central section with a pair of upwardly extending longitudinal arms with outwardly facing tabs. At the bottom edge of the rectangular section are a pair of downwardly facing arms that have inwardly facing tabs, and the top arms hold the bottom arms of an adjacent rail. An aggregation of arms are joined together side-to-side to form the side wall of a truck body.