An item specifically designed to fit into or over the openin (s) of various items to provide mechanical protection and/or to prevent the entrance of foreign matter during painting, shipping, storage, or the like. It is not designed to retain fluids under pressure during equipment operation. For items designed to fit only into an opening, see plug (as modified) and stopper (as modified). For items designed to fit only over an opening, see boot (as modified); cap (as modified); cover (as modified); and hood (as modified) .