♥ A 7 4
♦ 8 4
♣ A 8 5
| WEST | NORTH | EAST | SOUTH |
| 1♠ | pass | 1NT | |
| pass | 2♣ | pass | 2♠ |
| pass | pass | pass |
North opens 1♠.
With 9 points and a doubleton ♠ South must respond 1NT.
In standard bidding North would happily pass a 1NT response.
But in 2/1 the 1NT response is forcing for 1 round. North is forced to bid a 3-card minor so he says 2♣.
South prefers ♣ over ♠ but must allow for the possibility that North has bid a 3-card suit.
So South gives a preference to 2♠. This is called a "false preference", but it assures the team of being in at least a 7-card fit.
North happily passes and the pair lands in a reasonable contract, probably better than 1NT.
Deal 25
♥ 9 8 6 3
♦ A 7 6 2
♣ K Q 3