When you walk into the gym I go to, you have to scan your membership card in front of this little lens, kind of like at the supermarket checkout. There is a sign next to the lens that clearly says: HOLD CARDS 3 INCHES AWAY FROM SCANNER.
On Saturday, I was waiting to scan my card behind this guy who was waving his frantically just a breath away from the lens and started whining to the attendant girl "It's not working." The girl looks up and says that he's holding the card too close to the scanner. "But it says 3 inches awayyuh." Yeah, she replies. You're holding it too close. So he looks at her skeptically and slowly creeps the card backwards. When it was about 3 inches back, voila! It worked.
I couldn't help myself. When I went up to scan my card 3 inches from the lens, I said to the girl, "I worry about a man who thinks that's how long three inches is."