<P> No run may score on an inning - ending play in which the third out is a force out or on the batter before he reaches first base . Put in other words, force outs count before runs are scored . It is common that a runner reaches home plate a moment before the third out is made by force out . Such a case is routine; the runner doesn't score but is counted as left on base . </P> <P> It is also common that the third out might come on a non-force tag out after another runner reaches home plate . By extension of these two rules, the "fourth out" covers the case where the third out is not a force out, but a subsequent out is . Since the force out counts before the run scores, it must also count before the third out . </P> <P> Apparently there are no known MLB examples of a fourth out changing places with a prior out and thereby cancelling a run . The situations where a fourth out may be recognized are exceedingly rare, but some hypothetical examples, and two real examples where the fourth out rule did come into play, are noted below: </P> <P> Suppose three runners are on base with two outs, and the batter hits the ball within the field of play for an apparent hit . Two important facts are required: </P>

When does a run not count in baseball