A double lift is a sleight of hand

Sleight of hand

Sleight of hand, also known as prestidigitation or legerdemain, is the set of techniques used by a magician to manipulate objects such as cards and coins secretly....

 used by magicians

Magic (illusion)

Magic is a performing art that entertains audiences by staging tricks or creating illusions of seemingly impossible or supernatural feats using natural means...

 in card magic. It is a method by which the magician

Magic (illusion)

Magic is a performing art that entertains audiences by staging tricks or creating illusions of seemingly impossible or supernatural feats using natural means...

 can keep the identity of the top card

Playing card

A playing card is a piece of specially prepared heavy paper, thin cardboard, plastic-coated paper, cotton-paper blend, or thin plastic, marked with distinguishing motifs and used as one of a set for playing card games...

 secret by lifting the top two cards at once while making it seem as if only the top card is displayed. Hence, the audience is tricked into believing that they are shown the top card in the deck where in fact they are shown the second card. There are different ways to perform this sleight, many of which allow variations such as a triple lift or even a quadruple lift (turning over three or four cards over as one respectively).

Some versions of the Ambitious card

Ambitious card

The Ambitious Card, or Elevator Card, is a magic effect in which a playing card seems to return to the top of the deck after being placed elsewhere in the middle of the deck. This is a classic effect in card magic and serves as a study subject for students of magic...

routine rely almost entirely upon this sleight. In combination with a few other mechanics and good showmanship, entire acts can and have been made out of this single move.