This article is from the Car Audio FAQ, by Ian D. Bjorhovde (email@example.com) with numerous contributions by others.
Check the protective paper covering for any rips, tears or folding at
the time of purchase. In most cases if visual inspection is not done
at the place of purchase, it's very difficult to prove product defects
or damage done by the seller.
Inspect all surfaces that will come into contact to reduce tearing and
scratching of the protective paper covering and the Plexiglas finish.
Make sure that the protective paper covering remains in place until all
machining and milling tasks are finished.