Deal 7
 
  3NT
♠ K 7 3
9 6 4
K J 6
♣ K J 9 5
 
 WEST  NORTH  EAST  SOUTH
1NT
pass3NTpasspass
pass

The bidding has been as shown.
Partner led the Q, dummy played the 4 and it is your play.

When you have made your choice click NEXT .

Q

♠ J 9 8 5
K 7
9 7 4 3
♣ 8 7 2
 


 

 
Deal 7
 
  3NT
♠ K 7 3
9 6 4
K J 6
♣ K J 9 5
  Play the K.

Admittedly you have a terrible hand. But that's no reason to be careless. YOU can beat this contract, but you have to do it right now by unblocking the K. If declarer holds up you will continue with your 7 and partner will establish his suit while he still has the ♣A for an entry. If declarer doesn't hold up it will be just as bad for him.

But suppose you say "Well, partner's Q is just as good as my K so I'll just save the King for later" as you play low.
Declarer will love you. He will hold up on the Q, then again on trick two when you play the K. AND HE WILL STILL HAVE HIS A when you switch to another suit. He will have time to drive out the ♣A while he still has s stopped.

It was a good thing you held the K rather than declarer, but it is a nuisance that you must get out of the way on the very first trick.

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