Card marking

Card marking is a way that some card-playing games like poker can be cheated. It means making tiny but noticeable marks on the back of cards to help the person who made the marks to remember that card or the card's value. This helps the person cheating remember which cards have been played and which are still in the deck so they can have an advantage over the other players. Card marking is illegal and if you are caught doing it at a card game you can get in serious trouble.