Aluminum underbody semi-truck and trailer toolboxes and trcuk boxes. Underbody boxes are super heavy duty, high capacity and offer easy access from side of semi-truck. Boxes can be mounted in several ways including on the side of a trailer frame, under a trailer deck, or on a semi-tractor. These boxes are perfect for storing your equipment, like chains, binders, straps, tarps or your personal gear or tools. Underbody boxes are available in different sizes and can be ordered custom size.