Rust-oleum, gallon, black, plastic roof cement. fibered, asphalt based which provides a strong and flexible seal that resists cracking. ideal for installing or repairing roof flashings at valleys, parapet walls, gravel stops, stacks, vents, monitors and similar applications. suitable for sealing cracks in exterior foundation and chimney walls. use with fiberglass, polyester fabric or roll roofing for permanent repairs. fast and smooth without stringing.