In the workshop, you often have many different sizes, types and grits of sandpaper.
An expandable office folder is a great way to keep your sandpaper organized.
Label manila folders for each kind of sandpaper you use, then file them all in the expandable folder.
Not only will this make the sandpaper easier to find, but it keeps it flat and prevents curling due to changes in humidity.
Expandable folders are also a good way to organize tool manuals and magazine articles.