British Go Journal No. 56.  June 1982. Page 24.
Diagram 1 |
Many players are aware that among the most effective ways of blocking the progress of a group is the capping move (boshi), as shown in Dia.1, and know also that White can escape relatively easily against the direct contact play at A. When the situation is transferred to the second line, though, the same players who would find 1 in Dia. 1 very easily tend to overlook what is effectively the same play.
Diagram 2 ||
Diagram 3 |
Here are two examples from a recent game of mine. White 1 in Dia 2 threatens to connect up with his weak stones in the centre. It may seem natural to block at 1 in Dia 3, but that leaves white 2, after which the sequence to 8 is just one way to exploit Black's weaknesses.
Diagram 4 ||
Diagram 5 |
Dia 4 shows another example. The lower side is Black territory, and white 1 is a large yose play reducing it, Black 4 is an effective way to minimise the damage.
Dia 5 shows the common mistake in action again. Black cannot play 3' at 4, since he risks a huge loss in the ko when white cuts at 3. Black loses two points (at 5 and 9) compared with Dia 4. Note that black 7 here, which may appear to gain points in the centre, actually loses more on the edge since it wastes the opportunity of throwing in at 8, forcing White to protect against C after A, B when the dame are filled.
Diagram 6 |
Incidentally, for curious readers, the rather odd shape which occurs in both these corners arises from the "joseki" shown in Dia 6. (I omitted 11 and 13 in the second case) White's position is solid but awfully low, and I do not recommend this way of playing for White.