Vapor (Water) Shields

Be careful if you make your own in choosing material. Pulled door panels off a 70 Duster not long ago and the sheets were there but brittle and busted in a few spots. I talked to the owner and he had made sheets and installed them with the door panels 4 years earlier. Whatever the material was didn't last. I've seen perfectly good factory sheets that were 50 years old and still very flexible.