a net is located on the top surface of a truck trailer or box body on a truck that traps and holds in place snow or ice that forms on the flat tops of the truck or trailer . the mesh of the net aids in breaking up the snow or ice into smaller lumps and thus redices the hazard from sheet of ice or snow slipping from the top of trucks or trailers as they travel on highways . a plastic or rope mesh material held above the surface of the truck or trailer top is preferred .