Ducking in defence

Contract : 3NT
Lead : 6 of Spades

			8 3
			9 6 4
			K Q J 9 6 2
			7 2
	K 10 7 6 4	N W E S			J 9 2
	J 8 7				Q 10 5 3
	10 5 3				A 8
	10 5				K J 9 4
			A Q 5
			A K 2
			7 4
			A Q 8 6 3

The bidding:

South opens and noting that North has 6 points with a nice six-card suit, does not hesitate to bid 3NT, since the two hands also have 25 H points.
The declarer takes the lead with the Queen and leads the 7 of Diamonds to the Jack in dummy; we've guessed what will happen if East "plunges in" with the Ace to lead Spades: eleven tricks if declarer has the courage to do the finesse in Clubs (advice 22.1) …

When we "examine our conscience", the players in East must find for themselves the way they could have defeated the contract (advice 22.2) …: by ducking the 7 of Diamonds which results in going down by two instead of one or two overtricks …(advice 22.3).

You will have no trouble getting them to accept the principle of the day:

Show by an example on the board that it is possible to duck twice:

	K Q J 9 4
10 3		A 7 5
	8 6 2

South plays the 2 of Diamonds for the 3, the Jack and the 5.
He re-leads the King from dummy: if East takes it, South will have a Diamond left to communicate. So he must still play a low card (the 7) and only take on the third round (advice 22.5).

Ask your pupils if the duck would have been effective with, in North, the King of Hearts instead of the 9. They should reply no, since South can go and cash in his Diamonds thanks to the King of Hearts. Cutting the opponent's communications in a suit is only really useful if he can't communicate in the others! (advice 22.6).