Two guys were doing construction on a house. One of them who was nailing down siding would reach into his nail pouch, pull out a nail, and then either toss it over his shoulder or nail it into the siding.

The other guy, figuring this was worth looking into, asked, "Why are you throwing those nails away?"

The first guy explained, "If I pull a nail out of my pouch and it's pointed towards me, I throw it away 'cause it's defective. If it's pointed toward the house, then I nail it into the siding."

The second guy was outraged. He yelled, "You moron! The nails pointed towards you aren't defective! They're for the other side of the house!"