Courtesy runners can be used as part of high school baseball game speed up rules. Most states use this option, so umpires must know the rules regarding courtesy runners.
A courtesy runner is someone who is not batting in the game and can be used to run for the pitcher or catcher. This allows the pitcher and/or catcher to get back on defense more quickly when the half-inning ends. The courtesy runner remains a regular substitute who can come into the game as a fielder or batter.
Here are the rules regarding a courtesy runner:
The same courtesy runner cannot run for the pitcher and the catcher. A courtesy runner runs for the position, not the player. Thus if a pitcher is moved to the catching position and then gets on base, he must have a different courtesy runner as catcher than he did as pitcher.
Any player who has played in the game cannot be a courtesy runner.
If a player participates as a courtesy runner in a given inning, he cannot go into the game as a batter in the same half inning.
If a player bats for the pitcher or catcher, that player is not allowed a courtesy runner if he reaches base.
A courtesy runner can be replaced on base by another courtesy runner.
The plate umpire must record any courtesy runner’s participation.