GlasPly® IV is a specially constructed ply felt that is formed by coating a JM wet-process fiber glass mat with a light film of asphalt which is then surfaced with a liquid parting agent that prevents the roll from sticking to itself, while providing a clean, easy-to-mop surface. Laying lines are applied on the top surface of the felt so it can be installed with the exposure needed to provide the correct number of plies required by the specification.