Marked Deck For Playing Cards Trick
For as long as there have been playing cards, there has been players looking to mark them in some way so that they can cheat (with the exception of, maybe, magicians). It does not matter the game; blackjack, poker, baccarat, war and so on. Any card game where it is important to know the values of the cards you will find cheaters trying to mark them.
To get marked cards into a game, a cheater will do one of three things:
Mark their own cards, and then try to integrate them into the game. That could mean integrating individual cards, swapping decks or giving fixed decks to inside dealers (accomplices).
Mark the cards while playing.
Have someone else mark the cards in advance, leave and then the cheater sits down to play with the marked cards already in circulation.
Each comes with it is own pros and cons. More importantly, however, is how they mark them. There are a lot of ways to mark cards, and I am sure card markers are coming up with more ideas all the time. The biggest challenge with card marking is that many casinos do now allow you to touch your cards, which is usually the case with blackjack. So just touching your cards can arouse suspicion. So in those cases a cheater would either need to bring his own deck in, pass on this method or find a different game where the players can touch their cards.