| * | Incomplete territories | |
| There is a defect in Black's enclosing wall in Dia. 1. Black has surrounded the corner territory with his stones, but his wall is not complete. If you take a close look, you see that the two marked black stones are not linked: stones diagonal to each other don't make a connection. If White plays on Black's defect here (marked in blue), he puts two black stones into atari and captures them. |
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| Dia. 1 | ||
| In cases like this, Black has to reinforce and eliminate the defect by connecting, that is, playing a stone on the point marked in blue. | ||
| * | Finding imperfect enclosures | |
| Dia. 2. Black's territory is not perfect. Can you find the defect in his enclosing wall? | ||
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| Dia. 2 | ||
| Dia. 3. The defect is the point where White plays 1. Black's three stones here are put into atari and captured. If Black reinforced by playing a stone here before White plays 1, his territory would be complete. | ||
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| Dia. 3 | ||
| * | If you don't answer, the opponent comes into your territory. | |
| Dia. 4. This is a first-line endgame play. White has just played at 1. How should Black respond? | ||
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| Dia. 4 | ||
| Dia. 5. Black 2 and 4 are the correct moves. |
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| Dia. 5 | ||
| If Black omitted the move at 4, White would play an atari at the same point and break into Black's territory. If Black omits 4, he is surrounding territory with stones on a diagonal. You have to watch out when you surround territory on a diagonal. You must check to see if you need a reinforcement. |
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