In
poker jargon, "catching a hanger" happens when you see the
dealer dealing cards off of the bottom of the deck. Cheating in a poker game is not only stupid, but it is dangerous. When playing with people that you do not know very well, if you get caught, you are probably going to receive a
severe beating.
The benefit of dealing off of the bottom of the deck of cards is that you can give yourself, or someone that you are playing in cooperation with to
hustle people, the cards that you think you need to win the current hand. Of course it is rather difficult to rig the deck such that you know exactly where your cards are, so one must practice this evil art quite a lot to get anything out of it.
If you wish to know more about cheating at poker, I suggest you rent and watch the movie
Rounders or read all of
poker.