Don't toss those unwanted plastic cards that are always being sent you by organizations wanting your membership. Here is a great use for them in the workshop
Use 3M Stikit sandpaper, that paper with the sticky stuff on the back. Have a card for each grit of sandpaper that you use. I find the cards are perfect for doing those tiny repair jobs where you want to sand just a little blemish out and refinish. The cards bend, they allow you to get right up to tight edges, and if you have an array of them in different grits ready to go, it makes little fixit jobs so much easier and quicker.