Bridge Chestnut 1 - "Always cover an honour with an honour"
This chestnut is often wrong. The chestnut should be: "Cover an honour with an honour if it can promote a card in with your own or partner's hand"
Suppose the layout is
Here it would be an error to cover declarer’s Queen. You can outlast dummy and make your King. Cover the Queen and the entire suit is lost
Here, declarer in a 4-4 fit, advances the Jack. Should you cover? The answer is No!
Covering cannot promote a card in your hand or partner’s hand. Let declarer fish for your Queen. That is what he is looking for. However, if you had to think about it, declarer sees your flinch and knows you have the Queen. When dummy came down, you had to decide immediately:-
What am I going to do if declarer leads the Jack at me? A plan is the key!
Here, you should cover the Jack. If you don’t, declarer’s next card will be the two. Now, your King will “Beat the Air”. It won’t capture a decent card with it. Declarer has erred here. He has insufficient stuffing in the suit for this finesse. i.e. He has too few cards surrounding his honour. Instead, he should have played small to the Queen and then the Ace. No Loser!