Baseball Rules and the Baseline

Fair or foul? Baseball's baseline rules provide fans with the answer.baseball park image by Dave from Fotolia.com

The baseline is one of the most contentious areas of a baseball diamond. Some of the hardest calls an umpire makes over the course of a game involve whether a batted ball was inside the baseline, making it a fair ball, or outside the line, making it a foul. Most baseball leagues have standard baseline rules that help determine whether a ball is foul or fair.

Infield Plays

If a batted ground ball crosses the baseline and travels into foul territory, it is ruled foul and no play can be made. A player may catch a pop up that crosses into the foul area. If it is dropped in foul ground, it is ruled a foul ball and the at-bat continues. If it is dropped in fair territory, it is ruled a fair ball and the batter may advance to first base. If a batted ball begins in fair territory -- either on the ground or in the air -- and is knocked into foul ground, it is ruled fair and the batter may advance. When running to first base, a player must remain on the foul side of the line as he approaches the base or he will be ruled out.

If a ball is hit sharply down one of the baselines and it crosses the corner base (first or third) in fair territory, the umpire will point towards the field of play to indicate the ball is fair. Pointing away from the field indicates a foul ball. If a fielder makes a play on a ball down the baseline and touches it with his glove, the ball is ruled fair. A fly ball that hits the ground in fair territory and then hops over the fence in foul ground is ruled a ground-rule double, and the batter is awarded second base.

If a batted ball makes contact with either the left- or right-field foul pole, the batter is awarded a home run. The decision isn't as academic when the ball is hit high enough to clear the pole. The umpire can use his discretion to determine whether the ball was in fair or foul territory at the moment it cleared the pole. Major League Baseball began using instant replay for home-run reviews in 2008, allowing the umpires to stop play while they look over video footage of the home run. Most leagues do not have the luxury of replay, in which case the call is left to the umpires.