Obstruction is when a batter or runner has right-of-way and a fielder hinders him. When obstruction happens, the umpire calls it but lets the ball remain in play (do not call “time”).
After the play ends the umpires can award any bases that would counteract the obstruction. Every runner who is obstructed must get at least one base beyond the obstruction, whether as a result of the play or by an umpire’s award.
Obstruction includes the catcher interfering with a batter who is trying to hit the ball (this is called catcher’s interference under the Official Rules). It also includes a fielder trying to field a throw who does not yet have possession of the ball.
If a fielder fakes a tag, it is obstruction. The team is warned not to violate this rule again. If someone does so, the player is ejected.
Obstruction can also be verbal, such as a fielder telling a runner to go back a base because a ball was foul when it actually was not batted.
[OBR: ball is dead when there is “Type A” obstruction: play is being made on the obstructed runner at the time of the obstruction. Catcher interference with batter is not obstruction. If a fielder is trying to field a throw, it cannot be obstruction unless there is intent to obstruct. A fake tag is not obstruction, and there is no verbal obstruction.]