Becky and Sally Ann were doing some carpenter work on a house. Becky who was nailing down house siding, would reach into her nail pouch, pull out a nail and either use it or throw it over her shoulder.
Sally Ann, figuring this was worth looking into, asked, "Why are you throwing those nails away?".
Becky explained, "When I pull out a nail out of my pouch, about half of them have the head on the wrong end, so I throw them away".
Sally Ann got completely upset and yelled, "You moron! Those nails aren't defective! They're for the other side of the house!".