Carpenter's Square

All you need to know about Carpenter's Square-29

Diagram 29.1: White to play

We've seen very similar patterns while studying Shape 23 and 24. Just to repeat here to make the series complete.

Diagram 29.2: Solution

is clearly the only move. is the best answer. is also the only correct move. The result is a ko.

Diagram 29.3: Black fails

is a poor answer. It's never a good idea to reduce your own eyespace. The corner is dead.

Diagram 29.4: Black fails

is useless.

Diagram 29.5: White fails

here is incorrect. is good. The corner would end up in seki.

Conclusion: Diagram 29.2 is the best sequence for both sides.