It provides a durable permanent watertight seal for joints subject to structural movement. May be used above and below the waterline. Use for sealing decks to hulls, thru-hull fittings, vinyl ports, sealing/glazing windshields and bedding marine hardware. Will adhere to metal glass, wood, Lexan, ABS and certain other materials. Can be removed without damaging gel-coat. Not recommended for ferro cement hulls impregnated wood or oil-soaked materials. Cures in presence of water. Acid free.