Roll of BU during appeal of check swing

[TxUmp]

Re: calling check swing from position A or B for right or left handed batter:

In 3-man mechanics, we teach that PU should appeal to the umpire on the line regardless of which side the batter is batting from. He has a much better angle than the man inside (Poaition B or C). Why not use the same theory in 2-man mechanics. BU in Position A has a better angle to judge whether the batter actually offered at the ball
regardless of which side the batter is on.

I agree that the angle is poor in any case with runners on base. It is better to go with PU in most cases. But there are cases where he is totally blocked out (catcher comes up on high inside pitch, for instance). If PU asks in that case and the batter obviously offered at the pitch, both of you will look much better if you "call the obvious" and allow the strike.