♥ A 4
♦ 9 5
♣ A K 8 7
| WEST | NORTH | EAST | SOUTH |
| 1♠ | pass | 1NT | |
| pass | 2♣ | pass | 2NT |
| pass | 3NT | pass | pass |
| pass |
North opens 1♠.
South has 11 points, enough to respond 2♣, (or 2♦), in standard bidding, but not when using 2/1. So she bids 1NT.
North is forced to bid again, but unlike the previous hand, here he wants to keep bidding.
He bids 2♣.
South knows North doesn't have ♥s, so she shows her above-minimum hand by bidding 2NT.
North is happy to play Notrump. He assumes South must have something useful in ♦s and bids 3NT.
3NT seems to be a good contract. There are 8 top tricks and possibilities for a ninth winner in either ♠s, ♦s, or, (the best chance), ♣s.
Deal 17
♥ K 7 5 3
♦ A 10 3 2
♣ J 9 5 4