I have no idea whether or not this is an "official" Pente term for this type of situation, but "popping the cork" is how I always think of it. Some examples of it follow. It's relatively rare in my experience for it to show up in a game (it's showed up probably in fewer than 10 of the games I've played). Feel free to add or link to other games which you're aware of it occuring in. The threatened cork in the game below would be white stones played at O4 and O5 if black had been allowed to extend the blocked 3s into 4s.
This is a translation of a 5 min. + 2 sec. 15x15 board swap after 3 stones game which pente_gon and I played the other day; it's pretty obvious where the cork would go, I think (black stones at L7 and L8):
There are many game example of corks in the hammer line, but here is one early illustration of the possibility for it in that line:
Retired from TB Pente, but still playing live games & exploring variants like D, poof and boat
There's a popular saying in chess: "the threat is more powerful than the execution." This tactic definitely exemplifies that idea. I can think of many openings where white threatens to pop the cork, and black is forced to play a weak defensive move to prevent the devastation that would ensue. If you have a blocked tria (say K10-K9-K8 blocked on K11), with an additional stone on N9 or M8 it is often the case that threatening a "corked position" with M8 or N9 gives you enough initiative to win the game. Black would like to strongly block the tria with K7, but must instead play a weaker soft block on K6 or hand over the initiative by playing O10.
It's no use going back to yesterday, because I was a different person then.
Thanks for the insight on this threat, Karl. I'm probably under utilizing this threat as P1, I think. I ran across another one of my 15x15 swap 3 games where this happened, so it's likely come up in my games more often than I remember. I'll transcribe that one later today and add it.
Retired from TB Pente, but still playing live games & exploring variants like D, poof and boat
