Updated: Oct 2, 2022
You are West, defending against 2NT (only opponents bid: 1NT-2NT-Pass). Partner leads the heart 3. The HJ is played from the dummy:
1. First trick - What is the correct signal from your hand?
2. How many hearts does partner hold?
3. Trick 1 - South wins with the heart J. Declarer plays the 9.
Trick 2 - South plays a diamond. North's ace wins. Partner plays the DJ.
Trick 3 - North continues another diamond. Partner plays the DQ. South's king wins.
Trick 4 - South plays a 3rd round of diamonds. You win with the D10.
Trick 5 - You continue with a heart. Declarer wins with the HA.
Then at trick 6 Declarer plays the SQ. Partner and dummy follows. YOU?
4. AFTER seeing the solution and the whole deal - What is the declarer's mistake playing this hand?
Scroll down for solution and explanations
Gino's suggestion and explanation
1. Defending against a NT contract, when the third-hand defender cannot play a high card, then the correct signal is COUNT. Playing standard carding, the highest card (the 8) shows an even number of hearts. Playing upside-down carding, the lowest card (the 4) shows an even number of hearts.
2. Partner holds exactly 4 hearts. When playing 4th best leads, the heart 3 being the lowest card (The 2 is in the dummy) indicates a 4-card heart suit.
3. Do not win with the SA. Declarer wants to enter dummy's remaining diamonds via promoting the SK. Disallow declarer to enter the dummy by saving the SA to dummy's SK. If declarer plays the CK, you should do the same with the CA. You do not hold 6 winners to defeat 2NT (2 aces, 1 diamond and 2 hearts). So you should focus instead on preventing declarer from taking his/her own winners.
4. Declarer's mishandled transportation in diamonds. Since declarer must lose a diamond trick, he/she should DUCK the first round of diamonds to retain transportation.