Metal structures that attach one side of the frame to the other side. The go from the front of the trailer all the way to the back. The floor of the trailer is attached to the top side of the crossmembers. Spacing between crossmember varies depending on the brand. Heavier cargo weight requires closer spacing while lighter loads do not. Keep in mind that the closer the spacing the more crossmembers required. This adds more weight to the trailer and can reduce payload capacity, depending on the number of axles and their weight capacity.
