It turns out that if you make a circle with your thumb and your index finger, and the guy next to you sees it, he's got 5 seconds to break it, in which case he gets to hit you, or fail, in which case you get to hit him.
Oh yeah, that's him alright.
Man! When I was in the 101st we did that all the time! I thought it was just something looney the guys there cooked up as I never ran into it anywhere else.
Tried it at my next unit and the folks would stare at this circle I made with my fingers like *I* was looney.