The Mechanic's Grip is one of many ways to comfortably hold a deck of cards. The mechanic's grip is a standard grip utilized primarily by magicians and card cheaters as it allows a sturdy and versatile means by which to hold the cards. Covering the deck with your hand allows you to do things you regularly would not, such as viewing the top card's face (useful in poker or blackjack) or lifting and selecting a card without the spectators knowledge (useful in card tricks).
Use of this grip often portrays the handler as a cheat or someone with above average ability at manipulating cards; for this reason it is rarely used by professional dealers. A mechanic is a card sharp who uses the Mechanic's Grip or other sleight of hand tricks to cheat at cards, often to cheat other players out of their money.
The fact that a dealer holds the cards in a Mechanic's Grip usually should not be the sole consideration when deciding to accuse a dealer of cheating, because many honest dealers hold the deck in this fashion. It is a widely-used method of holding the deck even amongst dealers who are not card sharps and are not cheating.
Refer to the picture at right for finger placements.
To form the Mechanic's Grip, first hold the deck in your hand in the same fashion you might hold a hammer or tool. The cards should be lying flat in your palm with the longer side of the deck lying along the fingers. Take your pointer finger and move it to the short side facing away from you. Take your middle finger, ring finger, and pinkie finger and place them on the long side of the deck. Finally your thumb holds the deck together on the long side opposite of the other fingers. With this grip, more of the deck should be covered by your hand, thus making it more difficult for spectators to see what you are doing.