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Clamp
   

[Diagram]
Diag.: Clamp.

Black 1 here is known as the clamp. Notice that it applies pressure on the two white stones.


[Diagram]
Diag.: Clamp?

TakeNGive: Is this Black 1 also the 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]
Diag.: 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 W plays at 2, B continues at 3 and 5 in the knowledge that the clamp at 7 is available. However, the point of including it in his book is as an example of good forcing moves - by W! The clamp is effective in that W can not prevent B from connecting. However, Takagi did not really consider how well W could do by using a sacrifice strategy. He may not have known that thirteen years earlier (December 1974) Sakata had beaten Kato in the 30th Honinbo League with the same sacrifice in the same corner position. (thank you GoGoD CD and Kombilo :-)


[Diagram]
Diag.: Moves 42 to 51

W's turn at 3 yields a free forcing move in the corner at 5 before continuing with 7 and then stopping B cold with 9.


[Diagram]
Diag.: Moves 52 to 54

Finally W ends the play in the upper right in sente with 1 and turns to 3 to expand the upper left territory now backed up by W's new wall in the upper side.
This example demonstrates the basic clamp which can be a very powerful move. Indeed here it gives B 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 W's disposal. B must have them in mind in choosing this type of clamp.

[Diagram]
Diag.: Moves 44 alternative

Note that W can not win by turning at 3 after exchanging 1 for 2. B 4, 6, and 8 make miai of 'a' and 'b'.


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