Abstract: A tonneau support system for the bed of a pickup truck can be interchangeably utilized between supporting a bed cover, supporting load bars to load lock cargo, or support tie down straps to tightly overlie cargo in the course of being hauled. The elongated side rails are secured against opposite walls of the truck bed and include side grooves in which to removably secure the perimeter of the cover, and apertures in which to removably support displaceable load bars for load locking cargo or alternatively to receive hook ends of a tie-down strap to secure a load when hauled.