A vehicle tailgate enclosure can be adapted for rapid assembly and adjustable width. The enclosure includes two side sections and a center section. The center section is formed as an assembly of two portions. The side sections can each comprise beams which are advanced into recesses of the center section and retained. The width of the tailgate enclosure can be adjusted by the depth of advancement of the beams into the recesses of the center section. The center section can be constructed of a plastic material while the side sections can be metallic, thus leading to cost and weight savings. The tailgate enclosure can be easily and rapidly assembled by hand using a single tool.