This is a true story. I was helping a friend(he is a contractor,carpenter) put a new roof on a friends house. We live in snow country so the roof is steep 6/12 pitch. We were laying plywood very slippery, as was stated the people that use the nail guns hold the trigger on all the time. He slipped, nailed into the side of his knee. He said it did not hurt at first. One of his workers who is a pretty tough guy saw what happend stepped up and said let me pull it out(2 inch nails ribbed). Pulled out his side cutters grabbed the head of the nail which was on the out side of his pants pulled as hard as he could. would not come out now he goes to the side of the foor throws up. This is all taking place on the top of a 2 story house,6/12 pitch 100 plus degrees. we got both to the ground and to the doctor. His knee would not bend the nail went into the joint. Fun day is sure was glad I said would help.