Abstract: An assemble-in-place storage container mounts in the space behind the front seats of an extended cab truck. The container contains bottom, side, front, back and top panels which are configured to form the body of the container, as well as divider panels to provide compartments within the container. The container mounts on the horizontally oriented metallic back supports of the folded down jump seats of an extended cab truck. The bottom panel is sized and shaped to fit over the "footprint" of the folded down jump seats, and side panels are hinged to the bottom panel and are collapsed onto the bottom panel. With the bottom panel in place, the side panels are extended to the vertical; the side panels having sloping front edges conforming to the taper of the back of the truck's seats. The back and front panels are then vertically put into place, and are locked into position by tabs which fit into slots in the side panels.