[David B]

Originally Posted by mbyron

Good question. You have to call this in a way that does not deny the defense their play on the other runner. As you know, the ball remains live here, and if you come up screaming obstruction everyone's going to stop.

The FED manual, if you're using that, encourages umpires to use the delayed dead ball mechanic (fist held out to the side). I'm probably saying "That's obstruction," not too loud, and holding my fist out during the throw down to 2B. That signals that I've got something -- and explains why I'm not signalling safe or out -- but I'm not shouting or killing the play.

At the end of playing action, kill it and enforce the award. Make sure both scorekeepers are aware of your call.

and of course get ready to eject the coach who don't understand the rules etc,.