Abstract: A trailer sidewall structural system comprises a plurality of interconnecting modules, with each module having a dissimilarly configured, pair of opposing elongate, lateral edges. Such pair of lateral edges are configured so as to have a first edge of a first module, engage and interlock with a complemental second edge of an abutting second module, the modules being otherwise identical. The complemental lateral lengths of each module form a pair of opposing keyways, that permit interlocking of the lateral edges of two otherwise identically configurated, planar modules, thus providing for a variable length of modules, as may be dictated by the longitudinal dimensions required of a trailer sidewall, and the transverse dimensions of each such module are being adapted to be secured to the deck and top rails located along the trailer sidewalls.