I don't know whether I saw it or dreamed it, a pickup having storage built into the exterior side of the bed, between the cab and wheel well. Between the side inner wall and outer wall of the bed is nothing but air. My '98 Chevy 1500 has about 6" in the upper area and 12" between the frame and outer wall in the lower area. I think a box could be hung using the cross supports of the bed. The problem I see is having a frame and door that matches the outer panel contour. Of course each make and model truck would have to be slightly different. Has anyone seen such a compartment or actually made one?