Checking Extension

    Keywords: Go term

Chinese 1: 拦 (lan2)
Chinese 2: 拆逼 (chāi bī)
Japanese: ヒラキヅメ (hirakizume), sometimes ツメビラキ (tsumebiraki)[1]
Korean: -

A checking extension is

  1. an extension with 'added value' or
  2. a move by the player that prevents an opponent's extension in a particular direction. [2]

This 'added value' of the first definition may take a number of forms, for example an implied invasion, a threat to the base of a group or preventing an opponent's extension in a particular direction.

Invasion next  

Here B1 aims at an invasion next at a.

Response to the wedge  

In this case White's response to B1 is entirely natural: allowing Black the big, attacking play at b would be a major loss.

Both of these are examples of checking extensions by Black. In the second case we can assume Black's play is sente; but not in the first. To qualify an extension must at least be 'almost sente', in the sense of having a major follow-up.

Charles Matthews

[2] A more detailed definition is given in Joseki Volume 1 Fundamentals, where too near stones are excluded, i.e., a checking extension must not be confused with a block or move of the type connection (such as string connection or kosumi).

RobertJasiek: Outside SL, the second definition is the only one I have - consistently so - seen used verbally or in English or German literature for checking extension. The "added value" then becomes "to prevent an opponent's extension in a particular direction". Every example confirms this.

Checking Extension last edited by on August 7, 2019 - 10:24
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