1. That portion of the flashing which is attached to or rests on the roof deck to direct the flow of water on the roof, or to seal against the roof deck. 2. A material applied to the base of a wall extending above a roof, as a protection for the junction of the wall, and the roof. The simple principle is to turn the membrane up along the vertical surface, so that the roofing forms a large watertight tray, the only outlets from which are the roof drains to dispose of the water. Bituminous felts are usually used for a bituminous roofing. French (Solin de base)