Transverse sill reinforcement for a truck bed and method of making a sill reinforcement

A sill reinforcement assembly is provided for a sill area of a pick-up truck bed that is supported on and connected to a pair of frame rails. A unitary one-piece aluminum reinforcement is secured to the frame rails below the pick-up truck bed by a frame bolt fastener. The unitary reinforcement includes a continuous tubular receptacle for the frame bolt. One or more transverse walls of the reinforcement are connected by one or more bridging walls to the tubular receptacle. The transverse walls are connected by one-sided fasteners to a laterally extending wall of transverse beams. The frame bolt extends through the truck bed floor, the tubular receptacle, the transverse beam and is secured to the frame rails below the pick-up truck bed.