20 AUGUST 1988, Page 46

TRINITY

The use of the lock in defensive play is a well- known strategy, much tested at Federation meet- ings. It is an easy manoeuvre to learn but its apparent simplicity has lead to the downfall of many a dogmatic player, especially when under pressure. The seven full-locking points (3, 6. 7. 8. 11, 13. 15) are not of equal force, and double or triple locks may induce weakness, whilst appear- ing to create strength. The experienced player will, of course, be aware of 'backing-up. as a safeguard, but a correct exchange can split open even the most carefully laid piege.

In our problem A has just played the interchange 5:6 to lock up the final free blue and simul- taneously free the red at cell 11. A has reasoned that the strategy is sound, believing that B will now be forced to defend the free red which would give A the Net, if targetted. Unfortunately this is a classic case of blinkered thinking, because B now has an unstoppable line of attack. B to play and Target in two.

Solution in next issue.