Here was the original problem:

West leads the 10♦️. How do you handle the ♦️s?
Solution–
From the lead it looks like East has K Q♦️. If you cover West’s 10♦️ with dummy’s J♦️ then your 9♦️ will be a second ♦️ stopper.
Here was the entire deal:

When this hand was played, Declarer ducked the first two rounds of ♦️s. He ended up winning three ♣️s, one ♦️, two ♥️s, and one ♠️. Seven tricks for down one and a 40% board. Covering the 10♦️ was worth one more trick and an 80% board.
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