Lesson 138 : Mastering Carpenter’s Square (1)
By Nam Chi-hyung
Have you ever heard of the Carpenter's Square? It is one of the most difficult life and death positions in Baduk. In addition, they say that anyone who masters this position must be at least a 5-dan since there are various types of Carpenter's Square. Before we go any further, I'll tell you a small secret. Whenever I am asked about the variations of the Carpenter's Square, I just say "it's a ko" without reading thoroughly, and this works most of the times. While there are plenty of different ways to make a ko with a carpenter's square, there is no difference in the fact that it ends up as a ko, no matter what. Well, let's take a closer look.
Diagram 1
Black's position is the famous Carpenter's square; we will start with the basic arrangement of the position, with white stones surrounding the black stones without any empty points. Black occupies a pretty big space and looks safe, but it is actually vulnerable to White's attack. As you may guess, A is the vital point for both White and Black. Furthermore, B and C can be good attacking moves for White when there is no empty point between black and white stones as here. In this lesson, A is the only concern.
Diagram 2
Although I said a Carpenter's Square ends up with a ko almost every time, Black 2 will bring a death. Up to White 7 is an Eye vs. No Eye situation, and the Black group is dead.
Diagram 3
The key move is Black 2. Now you are one step closer to a ko. Of course A is the same as Black 2.
Diagram 4
However, an error can still bring death to Black. Here, Black 3 is a mistake that turns the corner into a flower-five shape, which means Black is dead
Diagram 5
On the contrary, White's mistake can let Black live. White's bend at 2 looks quite similar to the one in Diag.4, but the result is totally different. The situation in the corner up to 7 is a seki with a bent-four shape, which means Black is alive. As White, you should be careful not to bend in the wrong direction.
Diagram 6
When White bends in the correct way, it is best for Black to turn with 3 and make a ko with 5, since it is impossible to block at 4.
Diagram 7
To butt at 2 is another way to lead a ko. The most important among White's moves here is 8. If White places it at 9, Black will make a seki by playing at 8. Both Diag.6 and Diag.7 end up with a ko, but the characteristics of the kos are different. I prefer the one in this diagram as White, because he will lose less even if he loses the ko.
Diagram 8
White 2 cannot make a significant difference. The key move is Black 5 and it's a ko up to 7. Be careful not to block at 6, which would turn the situation almost the same as the one in Diag.4.
The writer is a baduk professor at Myongji University and a professional player of the game.