A fair ball that is obviously fair is not signaled by the umpires; however, a fair ball that is ruled fair close to the foul lines is signaled by the umpire extending or pointing with his right arm towards fair territory (unless a home run, in which case the home run signal is given). On a fair ball, the batter attempts to reach first base or any subsequent base, runners attempt to advance and fielders try to record outs. A fair ball is considered a live ball until the ball becomes dead by leaving the field or any other method.
In retractable or fixed roof baseball facilities, a batted ball is a fair ball if it:
A ball striking or becoming lodged in the roof or suspended object in fair territory beyond the outfield fence is a home run, regardless of where it may land.