The rear cross sill is located below the tailgate. It ties the back of the bed together by being bolted crosswise from one bed side to the other. The rear sill has "brackets" welded in place. The bed-to-frame bolt passes through these brackets as it bolts from the wood to the frame. The strips and wood sit on the ledge that has predrilled holes for mounting. The rear cross sill protects the edges of the wood boards.
Made in USA.