Suppose you hear your partner open one spade. You, the responder (North) have: (s)Kxx (h)AKxxx (d)xxx (c)xx, and respond two hearts. Opener now bids three hearts, showing you a "double fit" in spades and hearts.

You have ten high card points, and presume that opener has at least 13, for a total of at least 23. Normally, that's not quite enough for game, but the double fit has increased the value of your hands. Can you go directly to four spades or four hearts on the theory that the double fit is worth 2-3 points, thereby bringing you to 25-26 (adjusted)? Or should you stop at three spades and let partner decide based on whether he has a minimum or more?

Suppose you were opener, and heard partner (responder) stop at 3 spades. You have (s) AQJxx (h)QJx (d)xx (c) Kxx. You assume that he has a bare 10, and you have only 13. Can you go to 4S or 4H on the basis of the double fit?