The tiger's mouth
The tiger's mouth is the cheapest insurance in Go: two stones one diagonal apart dare the opponent into the gap, because the intruder lands with a single liberty and is captured on the spot — the mouth bites. It connects without solidifying, keeping the shape light and the eye potential wide, which is why some version of it appears in almost every joseki of Chapter 11. Compare the plain connect: both keep the stones together, but the tiger keeps a tempo of flexibility the solid stone spends. White has just tested the jaws. Black to play: collect the toll.