Keep a Stack of Papers in Order Without Numbering Them

 I often find myself with a stack of papers that are either not numbered, or are several small series of numbers. Instead of writing 1-50 or so on the pages, I can do this is a matter of seconds. I can then put them in order of how high the mark is on the page.

(I made this for my father in a hurry. Please forgive the image quality.)