An adapter plate assembly for stocking a variety of different modular boxes includes a first adapter plate that has a plurality of protrusions to engage structural features of a first modular box. The first adapter plate has a plurality of holes each extending to accommodate structural features of a second modular box. A pair of first blocks is each of the first blocks is pivotally coupled to the first adapter plate to abut an outer wall of the second modular box. A second adapter plate has a plurality of openings to accommodate structural features of the second modular box. A pair of second blocks is each removably coupled to the second adapter plate to abut an outer wall of the second modular box.