What does the umpire hand signal obstruction mean?

The umpire hand signal for obstruction indicates that a defensive player has illegally impeded the progress of a baserunner. This signal typically involves the umpire extending one arm horizontally across the body while simultaneously raising the other arm above their head. Obstruction can occur at any base and results in the baserunner being awarded the base they were attempting to reach, or the next base if they were already past the base in question. The signal serves to inform players and spectators that the defensive team's actions were deemed unlawful.