A utility rack for a truck may be removably attached to the side walls of the bed of the truck. The disclosed utility rack discloses internal cavities for attachment bolts or other fasteners. The internal cavities allow the fasteners to be hidden under an access cover during use of the utility rack while also providing strong and secure butt joints between the ends of some of the components. The ends of the components of the utility rack may be provided with protrusions and sockets that interlock to improve the stability of flush butt joints between components. The utility rack may include closed-loop outer-boundary side frames configure to clamp on opposing side walls of a truck cargo bed, with a crossbar spanning the truck cargo bed between top rails of the side frames. The closed-loop outer-boundary side frames do not require internal vertically oriented support posts inside the outer-boundary frame.