dunster

They are boards that comic book collectors use to protect their comic books, used with a sleeve. They are usually advertised as acid free, but in reality most of them are only treated on one side and the other side is not acid free at all. Quilters wrap fabric around them so they can store the fabric upright (like books) on a shelf.

I've found that I can store my fabrics upright on the shelf without the board. Just the support of the other fabrics seems to be enough to keep the fabric upright. And if there aren't enough fabrics around it, it's time to shop.