The Black Diamond Tread Aluminum Contractor Truck Box is a slanted, double-level storage solution that mounts on top of your bed rails to save valuable space inside your truck bed. Its lightweight and corrosion-resistant black powder coated aluminum diamond tread construction assures long lasting use and durability. Choose either a single or double top door above the single bottom door. Your equipment is secured with four sturdy locking stainless steel compression latches and aluminum continuous hinges. The truck box is built to last with aircraft grade cable lanyards and a watertight gasket system.