Short version: I need a thin, light weight sheet of plastic, 24x24 inches. What key words should I be searching for? Long version: I am running saddle bags on my bicycle. When they are not full or full of the wrong stuff they roll and have been known to rube the tire. I am thinking a very thin, ridged sheet of plastic would separate the wheel from the bag at all times. I don't have very many tools with me so this must be able to cut the sheet with minimal tools. I assume I will attach the sheet of plastic to the bicycle rack with zip ties.