The hook is the most common move in arm wrestling. You are probably familiar with the hook, because it is the move that is used when arm wrestling is portrayed in bars and elsewhere on TV.
It is considered an "inside" move, meaning you are trying to beat your opponent's arm instead of his hand (as you do in a toproll). To be successful in a hook, you should be stronger than or at least equal to the strength level of your opponent. If you believe that you are not as strong as him or her, try toprolling instead.