Lesson 140: Mastering Carpenter’s Square (3)
When you solve a life and death problem, you often try all the possible moves in the position to find the answer. But, even in a small local position, it is a huge task to check all the possible moves. For example, you've seen only two attacking methods in a Carpenter's Square and several possible answers for each, and there are many more variations still left. Therefore, if you don't know the key points of the shape and if you don't know what the attacking options are, you will not find the answer in time during a real game.
Diagram 1
White's bend with 1 is another probable attack of the Carpenter's Square. As you may know, it is possible only when there is an ally such as the ▲-marked white stone here.
Diagram 2
Black 2 may be the move against White's bend that comes to every player's mind. However, that move causes a death to Black. White 3 is a brilliant move in this case and there is no way Black can save the group after White 5. It doesn't help Black's situation to play at A instead of descending down with 4. White will block with B against Black A, forcing Black to connect at 4 and then play 5. In both cases, the corner is an Eye vs. No Eye.
Diagram 3
When Black turns with 2, White's attachment at 3 is still a good move to kill the group. By carefully watching the sequence up to White 9, you might figure out that the two points, White 3 and 7 are vital in the Carpenter's Square.
Diagram 4
It is too late for Black to exercise his ace, namely Black 4, after the exchange of moves from 1 to 3. White 5 can still be the fatal blow, and Black's group is dead up to 9.
Diagram 5
Against White's bend at 1, Black 2, the response we already learned in Lesson 138, is a good move. White 3 can easily be expected, but Black doesn't need to worry. The only thing Black has to be careful is not to directly block with 9 against White 7. By turning with 8, the corner becomes a ko.
Diagram 6
Even when White bends as White 3 here, Black should not directly block against it. Although the sequence is different, the consequence in this diagram is the same as the one in the previous diagram.
Diagram 7
What if Black directly blocks against White's bend? As you see, now White can play 9, one of the vital points of the Carpenter's Square, and turn the corner into a flower-five shape.
Diagram 8
White 3 here may look scary, but it is a pseudo-good move. With a simple sequence up to 8, the black group lives with a dual-life situation. I hope you didn't forget that Black should bend at 6. If Black comes down at 8 without the exchange of Black 6 and 7, the position will become a ko after White playing at 6 and Black at 7.
The writer is a baduk professor at Myongji University and a professional player of the game