When are they out?

[DeputyUICHousto]

Originally Posted by NYBLUE

There is a signal (2 fingers across the wrist) that I assumed most of umpires used to indicate runner(s) in scoring position with 2 outs.
Recieving and mirroring this signal prior to the pitch or AB reminds:
- The BU to vocalize his out immediately when the tag occurs
- The PU to listen for the BU's out while watching the runner attempting to score.

Do many of you know of and/or use this signal?

I've never seen or heard of this "two finger across the wrist". It isn't in any umpire manual I've ever seen.