Abstract: Horizontal members have hollow interior spaces to receive vertical members and other horizontal members therein to stack the horizontal members with a low profile on the sides of the truck in a retracted position. Vertical members have a pivot at one end and a pair of pins at the other end slidable in horizontal grooves in the horizontal members. The vertical members pivot up spacing the horizontal members apart to form vertical side cargo support side walls. Cross braces at each end provide structural stability between the walls. Vertical braces at each end lock the verticals upright.