Abstract: An assembly tray is injection molded with an open bottom to provide access to articles supported by the tray during manufacturing. Gear teeth are included on the bottom of the tray in the shape of a timing belt for indexing the tray during manufacturing. Stacking ledges are provided in the rim on top of the tray so that one tray can be stacked on top of another without sticking. A torsion box is provided on the sides of the tray to provide torsional stability. The assembly tray can be selected from a stack of other trays, used in automated manufacturing and stacked in another stack. The assembly tray is particularly suited for assemblying components of tape cassettes.