The MMMMajor Bridge Bidding System has identified certain hands (referred to as Sustain hands – featuring a long suit headed by at least the Queen (be it a 7+-card Major or an 8+-card Minor), and at least nine (9) playing tricks in total) which can be bid with a very high success rate (over 96%, and in Slam of over 93%) and accuracy. These hands are opened 2♣, 2♦, 2♥ or 2♠ respectively. The system uses exactly the same bidding sequences to show these hands and bid them to their conclusion, regardless of whether the player is opening the bidding or responding to any other Opening bid. So, opening 2♥ shows such a hand, as does responding 2♥ over any of the other valid Opening bids. In the Minor suits and over all other Opening bids, such hands are shown by 3♣ and 3♦ respectively, and then bid by the same rules.
All Opening bids are forcing. None show the specific suit held by Opener, but rather suggests its strength in HCPs and its shape.
1♣ shows 13+ HCPs and no 4+-card Major, 1♦ shows 13+ HCPs and one (1) 4+-card Major), 1♥ shows 13+ HCPs and both (2) 4+-card Majors, while 1♠ shows 10-12 HCPs and an unspecified 6+-card Major.
All first responses to normal Opening bids are limited such that absolute priority is given to providing for Sustain Responses. What this means is that, over an Opening bid of 1♠ (10-12 HCPs and a 6-card Major), only 1NT (0-6 HCPs), 2♣ (10-12 HCPs) and 2♦ (13+ HCPs) are valid response – with 2♥, 2♠, 3♣ and 3♦ reserved to show Sustain hands as a Response.
When Partner has opened the bidding, a hand with a long suit described above and not quite nine (9) playing tricks, may be reassessed with a temporary discount (say, 2.5 tricks after 1♣, 1♦ and 1♥ (which all suggest Opener has 13+ HCPs), and just 1.5 tricks after 1♠ (with Opener just having 10-12 HCPs), and may then qualify to be bid as a Sustain hand.
Finding a fit in Majors is given high priority. An eight (8) card holding in Majors is considered suit agreement, while a nine (9) card holding is required in Minors.