Rust-oleum, gallon, black, wet roof leak stop cement patch. a premium roofing cement designed to seal and protect roofing system components. fibered, asphalt based sealant stops leaks in standing water and repairs roofing defects including blisters, cracks and punctures in wet or dry conditions. multi-purpose roofing sealer combines penetrating oils and plasticizing agents for a durable, sag resistant formula that spreads easily in cold weather and offers long lasting flexibility. apply directly to cold, hot, wet, dry or underwater surfaces with commercial roofing or shingled residential roofing systems.