Leak Stopper Rubber Flexx Liquid Rubber Coating Black is a tough synthetic rubber coating that is designed to seal and waterproof roofs, walls, gutters, interior and exterior foundations, boats, tents, machinery and buildings. It creates a water, moisture and air barrier on whatever surface it is applied to. It will not peel or crack, and bonds to metal, masonry, wood, painted surfaces and most construction products. You can use this coating to form a seamless layer of waterproofing protection that will stretch and deliver lasting protection to virtually any surface you can imagine.