Is that just a smudge on the card or is there a card marker at your table? Cheaters have learned how to mark cards in such ways that nobody at the table will notice. Professional cheats can mark the cards in ways that nobody will notice even if they look at the card closely. Markings on a card do not penetrate the center of the card. The cheat does not want the marking to be so obvious as to have light shine through it, allowing other players to see the marking.
For a cheat to mark a card, they must have had a chance to have possession of it. The easiest way for this is for the cheat to have had access to it prior to the game. It could be his deck or he could have had access to it for a prolonged period of time. However, there are other ways for the cheat to mark the cards without having to have had the deck before the game.
Markings are typically small alterations in the cosmetic appearance of a card, usually on the backside. This may include scratches on the surface, a slight bend in one of the corners, or even a small change in the actual design of the card.
Why would a cheat mark a card?
The cheat marks cards to help themselves win in a poker game. They typically mark the cards that will help them make decisions such as high cards in regular gameplay or game specific cards, such as wild cards, for other games.
There are four typical different ways in which a cheat marks cards. These include, but are not limited to, shading, daubing, corner crimp, and thumbnailing.
Shading involves using a fine pen to change the design of the card. The mark is very small and requires an acute vision to be able to see the mark. Only upon extremely close inspection can this be found.
Daubing is when a cheat uses a pen with special ink to mark the card and uses special sunglasses (usually red lensed) to see the mark. The ink is not visible to the others at the table, but it is visible to the cheat with the special red lenses. You can find both the dauber and the sunglasses at a magic store or online at stores such as eBay.
Corner Crimping is when the cheat takes a card and slightly bends the corner. This can be accomplished in most games by holding the deck when dealing the cards. The cheat typically slides the card away from the deck and bends the corner with their index finger or thumb. Not only can the cheat crimp the card while being the dealer, but in poker games, and other games where players hold the cards, the cheat can easily bend the corners of the cards while they are holding them in their hands.
The marking on the card can easily be spotted later by looking at the corners of all of the cards in player’s hands and in the deck. When the marked cards are in another player’s hand there will be a bend in the light on the card and the corner will lift itself up from the table itself. When the marked cards are still in the deck the bent card will create a small gap in the deck. Professional corner crimpers can shuffle all aces, kings, or any other type of card to the bottom of the deck and crimp all of them at the same time.
Thumbnailing occurs when a cheat takes his thumbnail and makes a small divit in the back design of the card. This can occur when the cheat is dealing the deck and peeks at the card to identify it. If the card is desireable, the cheat will mark it. Thumbnailing can also occur when a player holds the cards and sets them down (such as in poker) to subtly drive a sharpened nail into the card. The nail mark can be seen fairly easily because the shine of light that reflects off of the card is dramatically different.