Penknife: A penknife is a small pocket knife that was originally used to cut the quill of quill pens. Penknives, for obvious reasons, usually fold in on themselves to hide the blade's cutting edge. A penknife usually has only one blade but the "Swiss Army Knife" style penknife which has multiple blades and tools such as scissors are extremely popular.

Beware: In the United Kingdom you may be prosecuted for carrying an offensive weapon if you are caught with a penknife!