Card Peeking is a maneuver where the dealer looks at the top card of the deck before it is dealt. By doing this, the dealer can easily predict who will win the hand and even manipulate the deck by combining this knowledge with another maneuver such as second dealing to deal the card to themselves or a certain player at the table.
The peek is typically seen as a maneuver that is accomplished by the use of the Mechanics Grip. The cheat ensures that their thumb is stopping the top card from being pushed in the natural direction and carefully uses their smallest finger (and sometimes their ring finger) to push against the long side of the top card. After countless hours of practice, the cheat has learned to see the bottom right corner of the top card as it bends. With no more than a fast peek, the cheater now knows exactly what that card is.
However, simply knowing the card is not as effective as combining the knowledge with another cheating maneuver such as the second deal. Poker players need not worry about this in a brick and mortar casino as much as they do in a regular home game. But those who should really watch out are players of games such as blackjack, super nine, and other casino games. The usefullness of this technique is much stronger and the results are incredibly obvious.