Pat and Mick get a job on a building site and their first job is to fix fascia boards to the front of houses.
While they are working Pat notices Mick pulling nails out of his nail pouch looking at them, throwing some away and using the others.
After about Half Hour Pat shouts to Mick "What are you doing".
Mick said, "Inspecting the nails. If the heads are facing me I know the nails are alright, but if I pull out a nail and the point is facing me, I know the nail is defect and I throw it away".
Pat shouts back, "You bloody idiot, If the point of the nail is facing you it's not a defect it's for the back of the house".