Lesson 141: Mastering Carpenter’s Square (4)

We've seen the simplest example of the Carpenter's Square in the last three lessons. There was no empty point, and the shapes of both the defending and the attacking sides were flawless. From today, we're going to study more complicated versions of the Carpenter's Square. The meaning of the moves will change, and you will become more confused.

Diagram 1

The position we will study in this diagram lacks a stone at the x-marked point. Different from the one we dealt with in the previous lessons, this one is less artificial. In fact, we can often meet this position in a real game with a variation of a 4-5 point joseki. The sequence from 1 to 9 shows how this shape is made. Black 6 is played elsewhere.

Diagram 2

Of course, the empty point works favorably for Black rather than White, but it is still not possible for Black to avoid a ko fight to save the group. White attacks with 1, the vital point of this shape, and Black 2 is the easiest way to make a ko as you already know. The result will be the same, even if White plays A and Black answers with B before White's bending at 3.

Diagram 3

I expect that you already know why Black cannot block with 4 against White 3. Until now, nothing much has changed.

Diagram 4

However, White 3 here doesn't work when the x-marked point is empty. Now, Black is perfectly alive because he can play B when White captures Black 10 with A. If White plays 9 instead of playing 5 and 7, he can make a thousand-year ko, as you can verify yourself. However, it is obvious anyway that a direct ko is better for White than a thousand-year ko.

Diagram 5

When there is an empty point like this, Black 2 can also be a good move. If the x-marked point is filled, White can play 6 instead of 5 and kill the black group. However, now White 5 is the only possible move for White, and the corner turns into a ko.

Diagram 6

Another twist with no empty point at x and a bending with the △-marked stone is a second possibility. When White attacks with the vital point at 1, it's important for Black to attach from the opposite side of the bending as shown here. Now, White 3 is not a good move, because it allows Black to live. Owing to the △-marked stone, White 5 cannot be as powerful as before. Up to Black 8, Black lives with a dual-life situation.

Diagram 7

In this case, White should butt toward the △-marked bending move. Different from when there is an empty point, it doesn't help Black to block directly against White 5 with A. The optimal result in this case is also a ko.

The writer is a baduk professor at Myongji University and a professional player of the game. chihyung@mju.ac.kr