Ground rule double

[1] Major League Baseball (MLB) has a set of universal ground rules that apply at all ballparks, two of which award two bases to the batter and any baserunners:[2] Two bases can also be awarded per home park ground rules—rules created to provide for unique playing conditions of a specific ballpark.

For example, these rules cover balls that hit the ground in fair territory and land out of play, typically by bouncing over a fence or wall in the outfield.

However, should such a fair fly be deflected at a point less than 250 feet (76 m) from home plate, the batter shall be entitled to two bases only.

[6][7] In the early years of baseball, batted balls that cleared the fence in fair territory on the fly or after a bounce were counted as home runs.

[10] The last "bounce" home run in MLB was hit by Al López of the Brooklyn Robins on September 12, 1930, at Ebbets Field.

Outfielders raising their arms, due to the baseball going under or becoming stuck in the fence, resulting in a ground rule double.
Batted balls lodged in the Wrigley Field ivy are ground rule doubles.
Runners advance two bases from their location at the time of pitch on a ground rule double; umpires can only award more than two bases in certain instances of interference .