Peeking
In most casinos today, if the dealers have an Ace or a Ten-value card up, they play the hand through, and if they have blackjack, all double down, and split bets are returned to the players, who only lose their original bets. Since this wastes time and causes some player discontent, some casinos allow dealers to “peek” at their hole card to determine whether they have a blackjack. If they have blackjack, they immediately turn it over and take all losing bets, which saves time and aggravation.
Occasionally, you can find a dealer who “gives away” the value of his hole card (when he doesn’t have a hole card that completes a blackjack). This is called a “dealer tell”. You have to understand body language or psychology, but this has been one of the most consistent winning blackjack secrets down through the years.
Recently, technology has been employed to speed up the game. Several companies have marketed laser devices that will read the value of a card by slipping the edge of the card through a narrow opening. It tells the dealer whether that card is a Ten or an Ace, but not the specific value of the card. This allows him to complete the game without the knowledge of the value of the hole card, once again saving time, but also preventing dealer tells.