The deke (short for “decoy”), while infrequently used, is an infield staple. It involves a fielder acting as if he has the ball when it’s somewhere else on the field, in an effort to confuse baserunners into awkward hesitation.
Think Chuck Knoblauch, the Twins second baseman who, during Game 7 of the 1991 World Series, acted as if he was fielding a ball that had actually been driven into an outfield gap. His goal was to confuse Braves runner Lonnie Smith, who had been on first base. It worked; Smith was delayed enough to force him to hold at third on a double, and the Twins won, 1-0, in 10 innings.
There are, however, downsides to this ploy. The Code states unequivocally that infielders are never to put down late tags in instances in which they don’t actually have the ball. I explained it in my recent Q&A with the New York Times:
As an infielder, there’s a rule against throwing down delayed phantom tags (dekes in baseball parlance, short for “decoys”), which can cause runners into late, awkward slides with a significant potential for injury. Padres infielder Derrel Thomas did just that to Gene Clines in 1973, throwing his glove down at the last moment as Clines steamed in from first on a stolen-base attempt. The fact that the pitch had been ball four, giving Clines the right to the bag anyway, made the play patently ridiculous. Clines tore ankle tendons as the result of a hasty slide, and never fully recovered. Clines said that Thomas “did have a reputation for doing some things on the field that weren’t the way you were supposed to play the game.”
When it’s done well, however, it’s a thing of beauty. Edgar Renteria utilized a phenomenal deke in the Giants’ game against the Phillies Tuesday, that was the polar opposite of Thomas’ play on Clines.
Ryan Howard had doubled into the corner, and was taking his time loping into second—not noticing that right fielder Nate Schierholtz was hustling to the ball. Renteria could see all of this from his position, but chose to simply stand near the base, arms at his sides. His body language told Howard that no play was imminent.
When the throw arrived, however, Renteria sprung to get it, and slapped a tag on Howard’s backside. (Watch it here.)
Howard later called it a “mental lapse,” but the success of the play owed just as much to Renteria’s heads-up deke.
– Jason
The Baseball Codes 
Humberto Quintero (obscure, nonhitting catcher for Astros) and Pedro Feliz got a Nat asleep on third last night. The baserunner was poking back into third after the pitch and Pedro just kind of casually walked to the bag. Humberto flipped a fastball to Pedro which Feliz snagged at the last second and slapped a tag on the runner. Inning over. Beautiful. Humberto loves throwing behind lefties to pick guys off of first, but I had never seen him or anyone else pick a guy off third in that fashion. I didn’t know there was a term for it until I found this site.
Schierholtz has the best arm nobody knows about.He hosed a coupla’ guys last year with that free & easy stride that makes it look like the ball is’nt comin’…that is until you have to take a seat.