1960-1966 Bed reinforcing strip – GM Truck Bed reinforcing strip 1960 – 1966 bed reinforcing strip Cross sill below tailgate.Like a cross sill, these steel pieces are placed perpendicular to the strips and wood for support. The difference from the cross sill is that the reinforcement strips are shorter in height and they are bolted to the bed strips and angle strips only. Reinforcement strips “reinforce” the bed, but they do not attach to the frame. Bolt holes in the reinforcement strip determine the placement of the bed strips and wood. Made in USA!