Three-space extension

Three-space extension on the third line  

is the three-space extension along the third line, like other extensions a big fuseki point which creates a base for the group and prevents White from attacking around the same point. Compared with the two-space extension, the three-space extension develops more quickly, but has the obvious defect at a where White can invade, one of the many three-space extension invasions. This is always a consideration when making the three-space extension.

Three-space extension on the fourth line  

It is also possible to make the three-space extension on the fourth line.

Mixed three-space extension  

This three-space extension (J: dai-dai-geima-biraki) could also be called a very large knight's move extension; in the article three-space extension invasions it is described as a ‘mixed three-space extension’, and invasions at a, b, c and d are listed.

Three-space extension from a wall  

Here, Black makes a three-space extension from a wall.

Completing the shape  

Black can follow-up with here to make a robust shape.

Developing with a one-point jump  

, a one-point jump, is another alternative for developing from the three-space extension.

Perfect shape  

If for whatever reason White plays the diagonal attachment at , Black's marked stone ends up ideally placed after the stand of (see extension from a wall). One line closer at a would be over-concentrated, that is, worse, from the point of view of good development.

Treating one stone lightly  

Depending on the situation, Black may also choose to treat one of the stones in the formation lightly for the sake of development.^[1] This type of sequence might be appropriate if White is strong in the upper right, as here. In that case Black a, White b might be good for White, and Black is better allowing in return for .

Variation  

If instead , gives Black a wall and nice shape.

Approaching strong stones  

Bill: In this particular situation, is problematic because it approaches White's wall, while extending only to a instead of allows White to play at b.

Prepare the way  

Bill: To avoid the problems of an immediate extension, - press against , preparing for a safe extension to .

Charles This idea of Bill's, to use the 3-5 point low approach, press, is a bit more subtle than may seem at first glance. For example, is held back one line, giving White much less chance of fighting on this side.