Falling asleep

Reading an article here about people falling asleep at work reminded me of some advice a friend once gave me:

If you want to sleep in your office at work do the following:
1. Lie on the floor.
2. Close your office door with your feet at the door.
3. Sprinkle paper clips on the floor in front of you.

If someone opens the door you'll awaken when the door hits your feet.
When they ask what you are doing on the floor simply say:
"I dropped a box of paper clips and was picking them up."