An Irish builder employed a young apprentice. His first job was to nail weatherboards onto a shed. The builder showed him how to align, support and nail the board, then turned away to start another job. A half hour later, he returned to see how the apprentice was doing.
Some progress had been made but the builder watched as the young man reached into his nail bag, drew out a nail, threw it over his shoulder, reached in again and drove the next nail. This happened a number of times. The builder, bemused, approached the apprentice.
“What are you doing, throwing away perfectly good nails like that?” he asked.
“Some of them are no good, you see. They have the points on the wrong end,” came the reply.
“No, no, NO, lad! You keep them for the other side of the building!”