Abstract: A sealing device for an enclosed cargo trailer comprises four integrally attached members positioned between the vertical posts and the cross supports of a cargo trailer structural assembly. The placement of the sealing device prevents particulates and fluids from being drawn up between the vertical post and the cross support and subsequently entering the interior of the trailer through the slit between the sidewalls and the flooring. In another aspect of the invention a reversible cross support is disclosed comprising three integrally formed members. A first channel is formed on one side of the first member and located proximate to its bottom, while the opposing side is also formed with a channel proximate to the top of the first member. The placement of these channels permits the cross support to be attached to and extend toward either side of the cargo trailer, thereby eliminating the costs associated with providing cross supports which can extend in only one direction.