Waist cut
The circled points show the weak spots of the keima.
If there are black stones near these weak spots, the spot farthest from the black stones is called the waist of the keima.
is the waist cut, striking at the waist of the keima.
The basic technique for White is to answer with hane at a, not push through at b.
This ( and
) is not necessarily the continuation, but by playing the hane away from the position, White limits the loss to
.
Not striking at the waist of the keima, but cutting at as in this diagram is zokusuji (vulgar play or bad style).
White's natural moves are good moves: blocking at , and either sacrificing
in order to make shape as in this diagram, or extending as in the next diagram:
If the surrounding position is strong enough, White can extend (stretch).
This is unlikely to occur, however, for if White were strong around, Black should not want to cut through the keima anyway.
Linguistic notes
The Japanese term tsuke-koshi is literally attach across, waist cut is not necessarily standard terminology. See strike at the waist of the keima / discussion page.
In Chinese, alone is called 跨 (kuā), the
-
-
sequence is called 跨断 (kuā duān). The character 跨 (kuā) means "straddle", and the character 断 (duān) means "cut".
See also: Sealing in by striking at the Waist
Authors: Dieter Verhofstadt, EGF 1 kyu