Mound Visits
Five per game, and a second visit to the same pitcher in one inning means he has to come out.
What it actually is. A team gets five mound visits per nine inning game, which includes visits by a coach, a manager or a catcher. If a manager or coach visits the same pitcher twice in the same inning, that pitcher must be removed. Visits do not count if they follow an offensive substitution or if there is an injury check.
What somebody who knows the game gets out of it. The limit was introduced to shorten games and it had a second effect nobody planned: it accelerated the adoption of PitchCom, the electronic signaling device, because a catcher who cannot walk out to fix a crossed sign needs another way to communicate. Sign stealing pressure and visit limits together pushed the whole sport toward electronic communication in about three seasons.
The numbers worth knowing. Five visits per game, one fewer than the original limit of six. Teams rarely use all five, and the ones who run out do so in extra innings.
What people get wrong about it. The catcher walking out to the mound is a visit. This catches teams out in tight late innings, and it is why you see catchers deliver messages from behind the plate or through the pitcher's glove rather than making the trip.
At Little League and travel ball. Youth rules generally allow more visits and use the same second visit in an inning means removal principle, though the count and the definition vary by sanction. It is one of the specific rule differences the four rulebooks feature on this site compares.
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