From Pepperl+Fuchs' Joe Kaulfersch:
1. Law of Mechanical Repair - After your hands become coated with grease, your nose will begin to itch and you'll have to pee.
2. Law of Gravity - Any tool, nut, bolt, screw, when dropped, will roll to the least accessible corner.
3. Law of Probability -The probability of being watched is directly proportional to the stupidity of your act
4. Law of Random Numbers - If you dial a wrong number, you never get a busy signal and someone always answers.
From 'Sound Off! Editors' Blog'