A trash rack (US) or debris screen is a wooden or metal structure, frequently supported by masonry, that prevents water-borne debris from entering the intake of a water mill, pumping station or water conveyance. This protects water wheels, penstocks, and sluice gates from destruction during floods. They are sometimes fitted to storm drain inflows and outflows to prevent debris from entering a natural watercourse. Other names used are trash screen (US) or debris grille.