As an maintenance man in an upscale hotel, I was asked to repair or replace the television in a guest room. When I arrived, the couple was watching a picture that had static lines going through it and was very fuzzy.
I knew all our spare sets were in use, so I figured what the heck, I struck the side of the TV with the heel of my hand. The picture became clear returned to normal.
"Look, honey," said the wife to her husband. "He went to the same repair school as you."