Ground rules (baseball)

In baseball, ground rules are special rules particular to each baseball park (grounds) in which the game is played. Unlike the well-defined playing field of most other sports, the playing area of a baseball field extends to an outfield fence in fair territory and the stadium seating in foul territory. The unique design of each ballpark, including fences, dugouts, bullpens, railings, stadium domes, photographer's wells and TV camera booths, requires that rules be defined to handle situations in which these objects may interact or interfere with the ball in play or with the players.

Major League Baseball has defined a set of "universal ground rules" that apply to all MLB ballparks; individual ballparks have the latitude to set ground rules above and beyond the universal ground rules, as long as they do not directly contradict each other. Additionally, a set of universal ground rules exists for the six MLB stadiums with retractable roofs, with the individual ballparks able to set additional rules.

The term ground rule double is often applied to a batted ball that bounces fair, then over the outfield fence in fair or foul territory, although some commentators and writers shun the term because league-wide rules, not ground rules, apply in this case.

Individual ballpark ground rules vary greatly from ballpark to ballpark. For the 2008 season, Kauffman Stadium, Yankee Stadium, and U.S. Cellular Field are the only MLB ballparks that do not have individual ground rules above the universal set.

Examples of ground rules of major league ballparks include:

These ground rules only apply at ballparks featuring retractable roofs. As of the 2012 season, these are: Rogers Centre, Chase Field, Safeco Field, Miller Park, Minute Maid Park, and Marlins Park. Rules governing batted balls striking the roof are defined in each individual ballpark's ground rules.

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