Signals And Discards

Board 3
South Deals
E-W Vul
♠8
♥Q 8 4
♦A K Q 4
♣10 8 6 4 2
♠K J 10 7 6 4 3
♥A 2
♦9 6 3
♣5
N
WE
S
♠A Q
♥K J 6 3
♦J 10 8 2
♣K Q J
♠9 5 2
♥10 9 7 5
♦7 5
♣A 9 7 3
WestNorthEastSouth
   Pass
3♠Pass4♠All pass
4♠ by West

Lead: ♦ A

North leads ♦ A, then ♦ K and ♦ Q. South discards ♣ 3 on the 3rd round to show an honour. North switches to a club to defeat the contract.