When a fielder holds a runner at a base to prevent advancement, what action does the umpire take regarding obstruction?

In the scenario where a fielder holds a runner at a base to prevent advancement, the umpire's action regarding obstruction is that the umpire signals obstruction and awards appropriate bases. This is based on the principle that a fielder cannot impede a runner's progress unless they are in possession of the ball and making a play on them. When a fielder physically obstructs a runner without the ball, it constitutes obstruction, which is a violation of the rules intended to ensure fair play and allow runners the opportunity to advance.

When obstruction is recognized, the umpire's role is to penalize the action to maintain the integrity of the game. This penalty often involves determining the last base the runner legally occupied and then awarding them an additional base, thereby allowing clarification on the runner's rights and ensuring that the team is not unfairly disadvantaged by the fielder's actions.

The focus on signaling obstruction and awarding appropriate bases reinforces the importance of protecting the rights of runners in the game, ensuring they have the necessary space to run without interference from fielders who are not in possession of the ball or are making an attempt to tag them out.