In baseball

Baseball

Baseball is a bat-and-ball sport played between two teams of nine players each. The aim is to score runs by hitting a thrown ball with a bat and touching a series of four bases arranged at the corners of a ninety-foot diamond...

, part of the infielder

Infielder

An infielder is a baseball player stationed at one of four defensive "infield" positions on the baseball field.-Standard arrangement of positions:In a game of baseball, two teams of nine players take turns playing offensive and defensive roles...

s' job is to cover bases. That is, they stand next to a base in anticipation of receiving the ball thrown from another fielder, so that they may make a play on an opposing baserunner who is approaching that base. On a force play

Force play

In baseball, a force is a situation when a baserunner is compelled to vacate his time-of-pitch base—and thus try to advance to the next base—because the batter became a runner. A runner at first base is always forced to attempt to advance to second base when the batter becomes a runner...

 or appeal play

Appeal play

In baseball, an appeal play occurs when a member of the defensive team calls the attention of an umpire to an infraction which he would otherwise ignore.-Appeal Play Situations:A runner shall be called out, after a successful live ball appeal, if he:...

, the fielder covering the base stands with one foot on that base.

In general, the first baseman

First baseman

First base, or 1B, is the first of four stations on a baseball diamond which must be touched in succession by a baserunner in order to score a run for that player's team...

 covers first base, the second baseman

Second baseman

Second base, or 2B, is the second of four stations on a baseball diamond which must be touched in succession by a base runner in order to score a run for that player's team. A second baseman is the baseball player guarding second base...

 or shortstop

Shortstop

Shortstop, abbreviated SS, is the baseball fielding position between second and third base. Shortstop is often regarded as the most dynamic defensive position in baseball, because there are more right-handed hitters in baseball than left-handed hitters, and most hitters have a tendency to pull the...

 covers second, the third baseman

Third baseman

A third baseman, abbreviated 3B, is the player in baseball whose responsibility is to defend the area nearest to third base — the third of four bases a baserunner must touch in succession to score a run...

 covers third, and the catcher

Catcher

Catcher is a position for a baseball or softball player. When a batter takes his turn to hit, the catcher crouches behind home plate, in front of the umpire, and receives the ball from the pitcher. This is a catcher's primary duty, but he is also called upon to master many other skills in order to...

 covers home base. On balls to the first baseman, the pitcher

Pitcher

In baseball, the pitcher is the player who throwsthe baseball from the pitcher's mound toward the catcher to begin each play, with the goal of retiring a batter, who attempts to either make contact with the pitched ball or draw a walk. In the numbering system used to record defensive plays, the...

 or second baseman might cover instead.

With baserunners on first and second, sometimes the shortstop will cover third on a bunt, known as the "rotation play" or "wheelplay."

Depending on the situation, however, various fielders can cover any base, sometimes an outfielder

Outfielder

Outfielder is a generic term applied to each of the people playing in the three defensive positions in baseball farthest from the batter. These defenders are the left fielder, the center fielder, and the right fielder...

 can even cover a base.

In American English

American English

American English is a set of dialects of the English language used mostly in the United States. Approximately two-thirds of the world's native speakers of English live in the United States....

, the expression "cover your bases" used outside of a baseball setting means to be thoroughly prepared for something.