A tandem masturbatory technique in which the participants lock arms at the elbows whilst gripping the shaft of their penises. They then flap elbows like a bird in synchronization to most efficiently share the work of jacking.
A sunburn or suntan focused on the left arm. It is caused by the left side of the body being the only half that gets exposed to sunlight while driving. Presumably, it would be located on the right side of the body in countries where they drive on the left side of the road.