The process of altering playing cards is known as card marking. This is a very effective cheating method as the marks are apparent only to the conspirator. After the marking process, the cards can be used for magic tricks on one hand, or for cheating in a variety of poker games, on the other. Usually the distinguishing mark or marks are done on the uniform obverse side of the playing cards, and in this way the effectiveness of the cheating is guaranteed. The easiest way to mark is called card bending. When using this method, the cheater marks the cards by crimping. Actually the first marks on the playing cards were crimps, bends or even tiny bumps, called blisters that resemble the Braille script. With the appearing of the first designs on the back of the cards, the cheaters started to alter the designs by using various inks or pigments. Adding or removing lines or patterns on the back of the cards is the most common method, but there are many others as well, such as block-out work, cut-out work, scroll work, shade work, tint work.
Card marking is often used to cheat when gambling or for card tricks, regardless of who shuffles and deals the cards. Sometimes additional manipulative skills are needed to steer the desired cards into the correct positions. No matter the efectiveness of the card marking, many casinos has invented a method to prevent cheating. By punching holes through the middle of the cards they sell to tourists, the casinos are trying to prevent the game tables from cheaters who are slipping the favorable cards into their hands when playing.