Coatings for weatherstripping must adhere to all of these weatherstrip materials. Foam or gasket weatherstripping can be applied to the sides and sashes. In the 1960s Schlegel introduced a continuous molded urethane process for foam weatherstripping. Weatherstripping can be used on windows to seal them on all sides. In later years, the cab doors had improved weatherstripping and electrically heated windows installed. Weatherstripping is also used on boats, to seal passenger and cargo areas from the elements. Door weatherstripping is particularly important for energy efficiency. Some of these doors receive custom weatherstripping at the factory. Exterior astragals are kerfed for weatherstripping. Weatherstripping can be placed around the windows to insure that the window is tightly sealed. The efficacy of weatherstripping can be significantly increased by specialty coatings during manufacture. Automotive weatherstripping can fail because of age or use. Schlegel started to make pile weatherstripping and plastic profiles for the building industry. The mute is held in the bell with weatherstripping.