Abstract: A removable cover for a pickup truck cargo box employing a standard 4.times.8 foot sheet of plywood to provide a second load level and a subjacent covered security area. A horizontally disposed channel is provided in the box front wall and stepped support surfaces are formed on the wheel housings. The tailgate has a horizontally disposed channel in its inner panel located in opposed relation with the front wall channel. The channels and wheel housing surfaces are sized to receive a standard rectangular building panel positioned with its forward edge in the front wall channel supported on the wheel housing surfaces in a horizontal plane. The panel's length results in its rearward edge being received and held in the tailgate channel upon the tailgate being pivoted to its upright closed position.