This is a convention invented by Eric Crowhurst to allow you to
rebid one no trump with 12 to 16 points.(or any other range you wish)
I'm sure he probably invented other conventions but this is the one most commonly
called just “Crowhurst”.
I have never seen the definitive description as he intended it to be played.
At my local club alone I know of at least three wildly different sets of meanings to all the bids.
It seems as if most people take the general principle and make up the sequences they like best
Nothing wrong with that, so below I give one possible set of bids and readily acknowledge they may
not necessarily be the best way to play the convention although it works for me.
Picture the hand ♠ A8, ♥ 98754,♦AQJ ,♣ Q98.
Playing 12-14 many would open 1 NT on the basis that the only rebid
after 1 ♥ -1 ♠
is 2 ♥
Playing this convention a 1NT rebid by Opener shows 12-16 points
2 ♣ from responder asks for further description
The responses as I understand them are:
12- to a poor 14 points
2♦ - nothing further to say,
may in some sequences show 4 Diamonds but doesn’t guarantee
2♥ or 2 ♠ either
repeating first bid suit showing 5+ or bidding partners suit showing 3 card support,
or bidding a new 4 card suit as in 1♦-1 ♠, 1NT-2 ♠ (enquiry); 2 ♥ 12-14 points and showing a four card heart suit
Good 14 to poor 15 points
2NT shows exactly a hand worth a poor 15 or good 14 and says nothing about distribution.
All bids by enquirer at the three level after this are forcing showing further description
Good 15 or 16 points
3♦ shows 5 of own suit and 3 of partners
3 of own suit shows 5 and denies 3 of partners
3 of partner’s shows 3 card support and denies 5 of own suit
3NT denies either holding.
Another little refinement if you can remember it is for opener to respond
3 ♣ (alerted and described if asked as forcing showing 5 of suit opened but not 3 of partners)
and then a bid of 3 of the opened suit shows 6 and not denying 3 of partners who can always bid their suit again if wishing to explore further
This is the way many of the players I play with and against play the convention with minor differences but I have seen it played where 2 ♦ shows 15/16 and then all bids are descriptive and forcing
As with a lot of conventions take on board the principles and work out what you are comfortable with.