Restorers Architectural urethane window and door casing are made up of both standard industry designs and new unique products. Urethane products are created by first spraying the inside of the mold with a barrier coat of primer. Liquid urethane is then poured into the mold, which is quickly shut and sealed. The urethane expands, hardens, and fuses with the coat of primer. The mold is then unlocked and opened, revealing a perfect duplicate of the original product, complete with a finished coat of primer. Urethane is lightweight and can be cut, drilled, screwed, and nailed just like wood and is available in many beautiful designs.