[greymule]

I have worked so often with three or four umpires that on certain plays we'll practically overrule the other without being asked. For example, runner slides in at 3B, BU from his position sees a tag out. But PU can see that the ball came out after the tag and then bounced back into the fielder's glove, but the runner's body blocked PU's view. PU will say right away something like, "You couldn't see it, Jimmy. The ball came out."

Same with a pulled foot at 1B, etc. It may not be the book mechanic, but when obvious wrong calls are corrected immediately, they're more likely to be accepted. But this kind of operation can work only with umpires who trust each other fully.

Never on regular safe-out calls at 1B or things like that. It would have to be on the type of call where the offended team is obviously going to be asking for an appeal anyway.