[nige1]

Deal, similar to this, from rubber bridge,
You are West, declarer in 6NT.
North leads ♠5.
Plan the play

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[Cyberyeti]

If N leads the 2♠ I call the director because it's in dummy. Assuming you mean the 5, my inclination is to cash a second spade, and if they break clear the spades in an attempt to remove an easy exit. I get more info on shape to make my subsequent decisions, and more chance of a defensive error.

[gszes]

Cyberyeti, on 2016-March-21, 16:57, said:

If N leads the 2♠ I call the director because it's in dummy. Assuming you mean the 5, my inclination is to cash a second spade, and if they break clear the spades in an attempt to remove an easy exit. I get more info on shape to make my subsequent decisions, and more chance of a defensive error.

Assuming nothing in the missing bidding has given away declarer's distribution -- running 4 spades might encourage a defender holding say 3 small clubs and 44 in the reds to abandon (pitch 2) clubs for partner to stop and thus hugely swaying the odds in favor of ducking a club.

[Winstonm]

I think low toward the heart Q is what I'd try. It forces a duck from the K yet still retains chances when the 109x are in one hand when the K is offside. Assuming K onside, there are interesting potentials due to holding the 7 and 8 of hearts along with a strip squeeze endplay if LHO holds 4 clubs and the heart K.

[robert2734]

Cash the spades and then duck a club. There are some interesting squeezes if you play a heart but none of them are with the odds.

[Winstonm]

robert2734, on 2016-March-23, 13:16, said:

Cash the spades and then duck a club. There are some interesting squeezes if you play a heart but none of them are with the odds.

I'm not so sure about that. Half the time the Q will hold the trick, and a club can still be ducked, giving a chance for club break plus a club/heart squeeze. When the heart Q loses, the count is still rectified for a heart.club squeeze if the 109x of hearts don't come down.

[robert2734]

If the QH loses and the clubs are 3-3, there's no squeeze. That's the down side. You do gain if there's T9x of hearts coming down or the same hand has long clubs and long hearts.

If the QH wins, you gain if north has long clubs and the king of hearts. Or if north has Kx of hearts. You break even if the clubs are 3-3 i.e. you still make your contract.

[rhm]

robert2734, on 2016-March-23, 13:16, said:

Cash the spades and then duck a club. There are some interesting squeezes if you play a heart but none of them are with the odds.

robert2734, on 2016-March-23, 17:57, said:

If the QH loses and the clubs are 3-3, there's no squeeze. That's the down side. You do gain if there's T9x of hearts coming down or the same hand has long clubs and long hearts.

If the QH wins, you gain if north has long clubs and the king of hearts. Or if north has Kx of hearts. You break even if the clubs are 3-3 i.e. you still make your contract.

My conclusion from this is that heart to the queen is the better chance.

It wins when North has the heart king and three or more clubs, since he will get squeezed between hearts and clubs after the club duck.
That North has 3 or more clubs is a 68% chance. So the overall chance for this happening should be close to 34%.
Discount one or two percent if you like, because if North has a majority of clubs there are more vacant spades in the South hand for the heart king.
If South has the heart king we need that the same hand holds 4 or more clubs and 4 or more hearts or that someone had 109 third or doubleton in hearts. I have not bothered to compute the exact odds for that but they are significant (around 15%).

If you duck a club you win when clubs are 3-3, roughly a 36% chance.
But if that is not the case residual chances are negligible.
You would need South to hold the heart king and someone to have at least 5 hearts together with the long clubs.
What is worse ducking a club means East can win and switch to a heart before you know whether clubs break.

Even if we discount the chance that North will go in with the heart king some of the time when you play to the queen the latter play looks to me clearly inferior.

Cashing spades first before you commit yourself is not unproblematic, even if everyone follows to the first 2 spade tricks.
What will you discard from dummy on the fourth spade?
A diamond discards from dummy hurts your squeeze chances after a heart to the queen.
Say the queen holds and you duck a club. Now opponents will return a club and there is no heart club squeeze any more.
Better to discard a club. But now ducking a club instead of playing to the heart queen will not provide enough tricks without the heart finesse.
You can only play 3 rounds of spades before committing yourself.

Rainer Herrmann

[gnasher]

Another reason for playing a heart is the restricted choice from the lead. With only small cards in hearts, or 109x(x), North might have led a hear.

[Winstonm]

Playing on hearts also yields the chance of reading the situation correctly when LHO holds Kxx of hearts.

[SteveMoe]

Best chance seems to be to play ♣ from West in order to duck a ♣ to North, and not South.

[oldem]

It looks as all hands are balanced. The opening lead of ♠5 cannot be a top of nothing, but the fourth best. Then beware of the ♥K offside. The best chance is to assume a 5-3-3-2 distribution for Clubs. Therefore, "duck a club" seems to be the best line.

[FrancesHinden]

Starting with a heart to the queen looks clear.
It's less obvious to me what to do if the queen holds.

Ducking a club makes when clubs are 3-3, or LHO is caught in a club/heart squeeze, or the HK is doubleton.
Ducking a heart makes when LHO is caught in a club/heart squeeze, or the HK is doubleton or tripleton, or the 109 of hearts are doubleton. (You can choose to pick up 109x of hearts on your right instead of Kxx on your left if you like, but I think the latter is more likely)

As all lines make with Kx of hearts, I think the extra chance of Kxx hearts on your left is only about 25%, so you are better off ducking a club.

[Winstonm]

After the heart Q holds, I think the play is to run off the spades while pitching a club from dummy. This might garner a little extra info. Suppose the spades are 42 and LHO has 4. Holding (presumably) 4 spades and at least 3 hearts, the likelihood increases that any club guard will be with East. If the assumption is accurate, the only hope then lies in transfering the threat by playing a heart to the J and hope LHO holds K10x, K9x, or Kxx or hearts.

Then, of course, the clubs could have been 3/3 all along. But what's the fun in that?