Lesson 139 : Mastering Carpenter’s Square (2)
By Nam Chi-hyung
In the previous lesson, we learned the most basic variations that would take place when the symmetrical vital point of a Carpenter's Square is attacked. In this lesson, you will see what else is possible for an attack, and the proper ways of defending.
Diagram 1
Apart from White's attacking move 1, the overall situation is the same as the one we dealt with in the last lesson. Before learning how to answer it as Black, remember that White 1 is only possible when there is no empty intersection between the black stones in the corner and the surrounding white stones. Since we already know that A is the vital point of the Carpenter's Square, let's start with Black's answer there. You still remember that most of the variations of this shape end with a ko, don't you?
Diagram 2
The sequence from Black 2 to Black 8 shows a way that turns the corner into a ko fight, and of course, this is the best result Black can get. You may wonder why White didn't play at A, which turns the corner instantly into a ko, but chose to bend at 5 instead. If so, then please check who will be the first one to take off his opponent's stone. In a ko, the most important thing is to be the first taker.
Diagram 3
Even if White bends at 3 directly without bending at A, the result will still be the same. The only thing Black shouldn't do is to block with 6 against White 3. If he does, the whole group will be killed by White's bending at A.
Diagram 4
Once again, you should be aware that there is no empty intersection between Black and White. In this case, Black 2 cannot be a good move. Up to 9, the corner is an Eye vs. No Eye position, which means Black is dead.
Diagram 5
Black's bending at 2 is even worse than the descending move on Diag.4, because it leads Black to death whether there is an empty intersection or not.
Diagram 6
Black 2 on the first line may seem possible since we learned this move as a good move when White comes in at the vital point, move number 5 in this diagram. Moreover, it seems that Black succeeds in making a ko with the sequence up to 10. But, this is an illusion.
Diagram 7
Against Black 2, it is good for White to bend at 3 first. If Black blocks with 4 immediately, White can kill the black group by turning the corner into a flower-five shape with the sequence up to 11.
Diagram 8
It doesn't help the situation for Black to play 4 against White 3. Now, the key move is White 5's descent down to the first line, rather than bending at White 5 as in Diag.7. Owing to this move, White can make the corner an Eye vs. No Eye position again and kill the black group.
The writer is a baduk professor at Myongji University and a professional player of the game.