There is a proverb that runs: A joy that's shared is a joy made double.
At the bridge table, if your partner doubles, it increases your chances of happiness and joy if you correctly interpret his message. In today's deal, East opens one club, your partner makes a takeout double, West passes, you advance with one diamond, East passes, and partner rebids one no-trump. What does that tell you about his hand?
To double, then to rebid a minimum number of no-trump, shows more strength than is required for an immediate one-no-trump overcall. South should have 18-plus to 20 high-card points. Then, with seven points, you are worth a raise to three no-trump.
After West leads the club seven, how should South continue?
Yes, East could have made his own takeout double over one diamond, but here it might not have worked well. South would have redoubled to announce his power, and one heart doubled would go down three, and two clubs doubled would be down two.
South has eight top tricks: three spades, three diamonds and two clubs. The ninth trick can come from diamonds (unless they are 5-0). Another way of looking at it is to realize that declarer has five tricks outside diamonds, so four diamond tricks are sufficient.
After winning the first trick, declarer should cash the diamond king, then play a low diamond from both hands (or duck the first round). South must allow for a 4-1 break, which will happen 28 percent of the time.