3-4 6-4 Enclosure
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The two-space high enclosure, also known as the AlphaGo enclosure, is a corner enclosure that was popularized by AI. It emphasizes outside influence at the expense of leaving the corner territory easily invadable. In many circumstances, Black is willing to take a local loss in exchange for benefits elsewhere on the board. This enclosure is very sensitive to the overall board landscape and a ladder, and it has many complicated variations that can result in fighting. Stone efficiency is an important consideration, and in many cases it can be inefficient for Black to invest additional moves to defend the corner after playing this enclosure.
Classically speaking, this enclosure was the rarest of the four enclosures. It does not appear in Essential Joseki, Enclosure Josekis, Ishida's Joseki Dictionary, Keshi and Uchikomi - Reduction and Invasion in Go, A Dictionary Of Modern Fuseki, The Korean Style or Kihon Fuseki Jiten. There is some discussion of this shimari in the Japanese book Shimari no Gihou (Shimari Techniques) by Ishida Yoshio 9p, published in 2002 by Kawade Shobou Shinsha, ISBN 4-309-26570-7. 
|Table of contents|
Moves are listed by frequency in professional games, which is sensitive to whole-board position. Bolded moves are commonly considered joseki.
- a, AlphaGo Enclosure, Small Knight Approach? - (common) (intermediate) (AI favorite)
- c, AlphaGo Enclosure, One Space Low Opposite Approach - (situational) (intermediate)
- e, AlphaGo Enclosure, Two Space Low Opposite Approach - (situational) (intermediate)
- f, AlphaGo Enclosure, 4-4 Attachment - (situational) (advanced)
- b, AlphaGo Enclosure, Hoshishita Splitting Move - (common)
- d, AlphaGo Enclosure, Hoshi Splitting Move - (common)
 Bob McGuigan: In his book Shimari Gihou referenced above, Ishida Yoshio gives quite a bit of information about this shimari and how to play against it. It came to notice during the Shin Fuseki period but now is not widely played. However, it is coming back a little due to the present-day emphasis on speed. Ishida devotes some 60 diagrams to the analysis of this shimari. Speaking of strategy, Ishida feels that from Black's standpoint the timing of when and how to defend the corner territory is a difficult issue. From White's perspective, helping Black solidify the corner territory is forbidden. White's goal is to exploit the weakness of Black's fourth line extension. Invading at in the following diagram is one idea. The most common response is followed by .
This tends to lead to White living in the corner and Black building strength on the outside or facing the upper side.