Karnak #170AF Tar Cement is ideal for emergency roof repairs when roof leaks occur since it can actually be applied under water. Karnak #170 Tar Cement is a tar base, plastic cement with unique water repellent characteristic. Prepared to a heavy consistency for application by trowel to provide a durable, elastic coating with long-lasting, weather-resisting protection, this product gives excellent performance over a wide range of temperatures and conditions and has excellent self-healing properties.