You know the little metal or plastic bit on pencaps? I used to think these were only useful if you put pens in your shirtpocket, or if you wanted to put it on your lip when you were bored during a meeting (a la Anthony Michael Hall in The Breakfast Club) but now I've discovered the real reason. I have a pen that's missing that little metal clip, and whenever I put it down on my desk it just rolls right off and onto the floor. Learn something every day.