When you have just one certain stopper (typically the ace), subtracting the number of cards you and dummy have from seven tells you how many times to duck. The purpose of the rule is to exhaust the leader’s partner of cards of the suit. However it is one of my least favourite rules (indeed it is a complete misnomer to call it a ‘rule’).

First of all, The Rule of Seven only applies when you have just one certain stopper, no more, no less, and if I had a pound for everybody I have seen use it in inappropriate situations, I would be ...[fill in analogy connoting wealth].

In (a) if you beat ♥ K with ♥ A, ♥ J10 will form a second stopper. Duck ♥ K and you will score just one trick*.
*It could still be right to duck ♥ K – and a second round – to keep West off lead with ♥ Qxxxx. But it will cost you your second trick.
In (b) you must beat ♠ Q with ♠ K. Duck and you’ll never make ♠ K**.
**Assuming the leader holds ♠ A, as is implied by East playing ♠ Q – although an expert East might play ♠ Q
from ♠ AQx.

 In (c) how many times would you duck if:

• (i) there was no E-W bidding?
• (ii) East overcalled 1 ♦?
• (iii) East opened 3 ♦?

(c) (i) West’s lead of ♦ 2 means he has four diamonds. With diamonds 4-4, there is almost certainly no point in ducking (and risking a more dangerous switch).

(c) (ii) East has five diamonds for his overcall; West has ♦Hxx [H = honour]. Win ♦ A on the third round to exhaust West of diamonds.

(c) (iii)East has seven diamonds, West’s ♦ 2 is singleton and you should win ♦ A immediately.

The point is that Rule of Seven is no substitute for working out the unique inferences of the individual deal.

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