HYDROBLOK backer board products are built with the same high-quality construction as the rest of our foam products with a 100% waterproof XPS foam core, covered by fiberglass mesh and then coated in a modified cement coating to provide superior strength and an excellent bonding surface for your tile, stone, glass or mosaics. All backer board can be easily cut with a utility knife, hand saw or small circular saw. They can be custom cut and can also be cut to bend around inside or outside corners. Backer board must be fastened with approved HYDROBLOK washers and screws which are available from your local dealer.