Rule 7.09 - It is interference by a batter or runner when - (i) in the judgment of the umpire, the base coach at third base, or first base, by touching or holding the runner, physically assists that runner in returning to or leaving third base or first base.
Play - Batter crushes a belt high fast ball and clears the
centerfield fence for a home run. While circling the bases the 3rd
base coach gives the home run hitter a congratulatory high five.
Should the umpire call the runner out for touching the 3rd base
Answer: As you can see by the wording above, it is NOT assisting the runner leaving third or returning to third, it is a happy moment and nothing should be done and certainly don’t call the runner out.
Play - Runner on 3rd base with less than two outs; the batter
skies one to deep left field, the base coach puts his/her hand on
the runners back and gives a little push to the runner when the ball
is touched. You are the umpire, what do you do now?
Answer: Call the runner out for the interference by the base coach.
Play – Runners on 1st and 3rd less than two outs and there is a base hit to the outfield. The runner on 3rd scores easily, but the runner coming from 1st is going to be a dead duck at home. The base coach at 3rd steps in front of the runner rounding 3rd to physically (with contact) hold him/her at 3rd base. The throw comes into 2nd base in attempt to get the batter-runner who is trying for a double. You are the umpire and you see all this happening, what do you do now?
Answer: The old delayed dead ball. You have seen the interference at 3rd base and you have that runner out, but you want to delay your call until you see if the defense is able to get an additional out at 2nd base. When all play has ended, call time and signal that the runner now at 3rd base is out and tell the world why he/she is out.