Overview
A ground rule double is awarded when a fair ball bounces into the stands or becomes lodged in a fence or barrier. The batter advances to second base, and all runners advance two bases. Unlike a home run, the ball did not clear the fence directly, so a runner on first stops at third instead of scoring, potentially limiting run-scoring opportunities. Each NPB stadium has its own ground rules; Tokyo Dome, for example, has rules for balls hitting the ceiling. Technically, a ball bouncing over the fence is an 'automatic double' rather than a true ground rule double, but in Japan both situations are collectively called 'entitle two-base.' These plays can be pivotal in close games, and borderline calls between home runs and ground rule doubles are subject to video replay review.