Ancient Times. In the original Roman system, a 2 opening showed any 4441 hand with 17-20 HCP.
The responses were the same as in their mini-Roman 2
opening: new suits were
signoffs (opener runs if that suit is their singleton), and 2NT is their strong
inquiry (opener rebids their singleton).
Modern Adjustments. Today, most players play that a 2 opening shows any 4441 hand with 16-20 HCP.
Some include 5440 hands, where the five carder is a minor. Also, some players
have decided that after the inquiry: 2
- 2NT; opener rebids in the suit below
their singleton:
3
(diamond), 3
(heart), 3
(spade), 3
(club).
The Blue Club system uses the 2 opening to show any 4441 hand with 17-24 HCP.
After the inquiry, responder can sign-off at any time except in the relay suit
(opener's short suit, except 2NT over 2 - 2
- 2
is considered the relay).
For 17-20 hands, (except for the 2
- 2
- 2
auction... see below)
The first relay ask asks for the range:
The second relay asks for controls:
The third relay asks for the number of queens:
For 21-24 hands, The first relay asks for the number of controls:
The second relay asks for the number of queens.
Over the 2 rebid, 2NT is used as a further inquiry: 2
- 2
- 2
- 2NT
Over these response, the next relay asks for controls; then another relay asks for number of queens.