Abstract: A support apparatus for auxiliary structural elements in a pickup truck. First and second frame members, each having a support element, a retaining element and a plurality of upwardly opening frame pockets, are supported on each sidewall of the pickup truck. Third and fourth frame members, similar in construction to the first and second frame members, are supported at opposite ends by the first and second frame members. The frame members form a deck-supporting enclosure in which an auxiliary deck may be clearingly lowered and received. The frame pockets of each frame member form a side-supporting structure in which a vertically disposed auxiliary side element may be clearingly lowered and received.