No matter how skilled you are or may become in the game of gin rummy, you stand no chance against dishonesty. Granted, there are certain specific rules of the game that, if followed, give you a certain level of protection against cheating. There are other procedures that if used consistently will give you even more protection. The most important thing is to know that you have the utmost confidence in the integrity of everyone in the game. There are times, especially when the stakes increase, the temptation to be dishonest grows. There are certain people who will take that dishonest advantage for the sole purpose of winning and satisfying their own egos. It is important to be on guard for both the person who is trying to win for money, as well as simply winning for pride.
Mechanical cheating is one of the ways to cheat. The items that are used by professional card cheats include shiners, embossing devices and marked cards. All of these are most effective in Gin, as in any other card game.
Shiners are mirror devices, usually concealed in a ring or similar piece of jewelry, which enables a dealer to read the actual cards that he is dealing out. Embossing devices, which are used to mark cards, can also be concealed in rings or bandages. It is easy to purchase marked cards which will permit the user to tell the rank of each card. Usually a small geometric figure is lightened, enlarged or darkened, or a line is thickened here or there. It could be anything that helps a player distinguish it, without being obvious to the non-cheaters. At one point there was even a marked deck that made it possible to identify the suits of each of the cards.
The most prevalent form of mechanical cheating is card marking. This does not by any means mean that an entire deck is marked. A player who is able to identify any one card in the deck has a tremendous advantage. If he is able to identify two or three cards, then this advantage is almost impossible to overcome. In order for an expert cheat to identify a particular card, all that he needs to do is to place a tiny nick in a card with a fingernail, an embossing device, or any other identifying mark. The only real protection that you have against this type of cheating, other than knowing who you are playing with, is to change the decks used as often as possible.
Detecting a player who is using mechanical cheating techniques requires expert knowledge and vision. Specialists in this field have produced clearly illustrated books which fully explain these tricks, and if you are going to play gin rummy competitively, you may want to read up on them, and the many gambling articles on the subject of card cheating. If you have any suspicions that cheating is going on you should leave the game immediately, because your focus would then be on the cheating, and not on the game at hand. Again, it is of the utmost importance, that you are well aware of who is playing in the game, and that you can trust them completely.