What happens if a pitcher turns his shoulders to check a runner at first base after making his stretch and winding his hands together?

When a pitcher makes his stretch and then brings his hands together, he has created a "set position," which establishes certain rules regarding his actions. If the pitcher then turns his shoulders to check a runner at first base, it constitutes a violation of the rules, specifically a balk. This occurs because once a pitcher is in the set position, he is not allowed to make any movements that could deceive the runner.

Turning the shoulders to check on a runner effectively makes it seem like the pitcher is preparing to deliver a pitch—which, following the set position, is not permitted if it creates ambiguity about whether he intends to pitch to the plate or attempt a pickoff. Hence, this action results in a balk, which is intended to prevent the pitcher from gaining an unfair advantage over the baserunner. Rules are designed to ensure that the game remains fair and consistent, and this particular rule protects the integrity of the pitcher's actions once they are in a defined position.