Comb Formation

Comb formation  

The comb formation is like a rectangular six, but with cutting points. On the side, it has cutting points at a. It is a basic life and death shape.

See The comb formation is alive.

Broken comb formation in the corner  

The broken comb formation in the corner or weak rectangular six in the corner has only one cutting point (a). See rectangular six in the corner.

Black first: It is alive with at .
White first: It is ko after as shown in the diagram.