Cladding is the application of one material over another to provide skin or layer intended to control the infiltration of weather elements, or for aesthetic purposes. Cladding does not necessarily have to provide a waterproof condition but is instead a control element. This control element may only serve to safely direct water or wind in order to control run-off and prevent infiltration into the building structure. This is also a control element to prevent noise from entering or escaping. Cladding applied to windows is often referred to as window capping and is a very specialized field.