All you need to know about Carpenter's Square - 27
Submitted by macelee on 2013-02-12 13:07; Last upda
ted on: 2014-05-08 13:05
Diagram 27.1: White to play
Can 
secure this corner?
Diagram 27.2: White fails
appears to be important, but 
can only start a ko here.
Diagram 27.3: White fails
has the option to fight an alternative ko. This way white takes the ko first which is a slight improvement.
Diagram 27.4: Solution
Making / 
exchange first is the correct order. Then white can come back to the key point 
and kill the corner - black cannot play 'a'.
Conclusion: Diagram 27.4 is a simple and elegant solution.
