Mini key-card Blackwood


- are used after a pre-empt in a minor suit at the 3-level.
- The inverted minor suit at the 4-level is question after key-car.
4C after 3D, and 4D after 3C.
1-step : 0 keycard, not queen of trump
2-step : 0 keycard, + queen of trump
3-step : 1 keycard, not queen of trump
4-step : 1 keycard, + queen of trump
5-step : 2 keycard, not queen of trump
6-step : 2 keycard, + queen of trump