Aluminum 5th Wheel & Flush Mounted Tool Boxes for Pickup Trucks. Highway Products started building specialized 5th wheel tool boxes back in 1980. They provide storage of tools, parts, supplies and recreational equipment for a special breed: People who travel. The "5th wheel box" is flush-mounted with the bed-rails of your pickup truck. The shorter "Partner" box, positioned at the tailgate, leaves plenty of clearance for your 5th wheel trailer king pin.