Scissors

From MidnightWiki

Scissors: if you want to sharpen a pair of scissors, cut sandpaper. 9/17

9/18 Here is more detail on this subject: sandpaper is a temporary fix only!

If your scissors become dull while you're in the middle of a project, a temporary fix is to use the scissors to cut through some sandpaper. The sandpaper will help remove burrs and partially sharpen the rough edge. For a more long term solution, you'll need to get them sharpened. Or you can just go buy new ones. Or forget scissors altogether and just use your teeth.

Scissors were invented by Leonardo da Vinci.