A cotton module is one type of a stack of agricultural produce. A tarp is specially folded and mounted on the back gate of a cotton module builder. As the module builder is moved off a completed module, the tarp is unrolled onto the top of the module. The tarp is tied down using ground cords, which extend along the ground underneath the module. The ground cord is mounted on spools on the side wall of the module and is placed under the side walls while the side walls are elevated upon the conclusion of a move from an old location to a new one. Then, when the module builder is lowered and the module is built, the ground cords are in place. The tarp' s sides are vented.