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Clamp
    Keywords: Shape, Go term

[Diagram]
Clamp.

B1 here is known as the clamp. Notice that it applies pressure on the two white stones.


[Diagram]
Clamp?

TakeNGive: Is this B1 also a clamp? (If White blocks at a, Black connects at b, and vice-versa.) Or is this called something else? Also, this seems to work only on the second line, I guess because the edge of the board is close.



DaveSigaty: This is indeed also a form of clamp. It is an important suji that frequently appears above the second line.

[Diagram]
Moves 35 to 41

This is Takagi Shoichi (Black) versus Kato Masao in the 43rd Honinbo League played in November 1987. Takagi uses it as the first example in section 2 of Beyond Forcing Moves.

When White plays at W2, Black continues at B3 and B5 in the knowledge that the clamp at B7 is available. However, the point of including it in his book is as an example of good forcing moves - by White! The clamp is effective in that White cannot prevent Black from connecting. However, Takagi did not really consider how well White could do by using a sacrifice strategy.

He may not have known that thirteen years earlier (December 1974) Sakata Eio had beaten Kato in the 30th Honinbo League with the same sacrifice in the same corner position. (Thank you GoGoD CD and Kombilo :-)


[Diagram]
Moves 42 to 51

White's turn at W3 yields a free forcing move in the corner at W5 before continuing with W7 and then stopping Black cold with W9.


[Diagram]
Moves 52 to 54

Finally White ends the play in the upper right in sente with W1 and turns to W3 to expand the upper left territory now backed up by White's new wall in the upper side.

This example demonstrates the basic clamp which can be a very powerful move. Indeed here it gives Black exactly what he wanted. Unfortunately he had not thought through the implications in this particular position well enough. As a result, the example is also a very good illustration of the resources at White's disposal. Black must have them in mind in choosing this type of clamp.

[Diagram]
Moves 44 alternative

Note that White can not win by turning at W3 after exchanging W1 for B2. B4, B6, and B8 make miai of a and b.


See also:



This is a copy of the living page "Clamp" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.