Plastic roofing cement is a spreadable compound made from ground asphalt. It is used for applying shingles and affixing flashing on a roof. It can be used for sealing joints, cracks and nail holes, and it is also called mastic, flashing cement and asphalt plastic roof cement.
Roofing cement can be applied from a can with a trowel or with a caulk gun when purchased in a caulk-type tube. The term "plastic," when referring to roof cement, means capable of receiving form or being molded. Therefore, plastic roofing cement can be formed to fit in corners and to fill cracks, crevices and hard-to-reach places.