Used only in the sequences:


1X - 1Y - 1NT - 2...9+HCP
or 1X-(1Y opp)-*(Partner)-1NT-2
or 1X-(* opp)-**(partner)-1NT-2

Opener's 1NT rebid shows a BALANCED 12-16 HCP adjusted precisely. With 17-18 Balanced bid 2N.
2 is the ONLY Forcing response. It requires a strict minimum of 9+ HCP. Note ALL other simple rebids are strictly NON-FORCING and should usually be PASSed.

Opener's continuations over a 2 response are:

3Y                Shows 3+ card Y(opp) and 15-16 HCP - a good guard.  Or good 3 card support for 'Y' partner
3               Shows an unbid 4 card Heart suit and 15-16 HCP in 2 specific sequences: [1 -1(spades)-1N-2  OR 1- 1- 1N-2]
3              Shows 16 HCP
3                Shows 4 card if a genuinely unbid suit and 15-16HCP . e.g: 1-1(hearts)-1N-2-3 or 1-1-1N-2-3
2                Shows a 4 card previously unbid heart suit. 1-1(spades)-1N-2- OR 1-1-1N-2- or similar
2Y                Shows 3 card support for 'Y' and 12-14 HCP or a good guard for Y(opp)
2Ma              Shows a GOOD previously unbid 4 card Major suit  - partner to bid 2N with good guard in opponents suit or an unbid suit
2NT              Shows 15 HCP [or a very good 14 but ONLY as long as 2 & 2Ma above are NOT valid]
2                None of the above, 12-14 HCP - a kind of negative - invites Partner to choose contract. If Diamonds have not previously been bid naturally then most likely to be a (3-)4 card Diamond suit and Partner may PASS

Now responder has a clear view of partner's strength and distribution, the final contract can be selected. Game can be bid or either a cue-bid of Y(opp) or a * of a further opponent intervention or bidding the 4th suit: are all gane forcing WHILE any other bid is strictly TO PLAY.