Conventions in depth
An artificial, game-forcing opening for the strongest hands, saying nothing about clubs.
An opening of 2♣ is artificial: it promises nothing in clubs, only great strength. It covers two kinds of hand:
Everything weaker is opened at the one or two level instead: 2♣ is rare, and when it appears partner knows game is nearly certain.
Because opener has yet to name a suit, responder’s first job is to keep the auction open, letting opener describe the hand first. Responder makes a positive reply only with real values:
Once 2♣ is opened, the partnership may not stop below game: opener describes, responder supports or shows values, and there is room to describe both hands. With a worthless hand responder can even signal it: after waiting with 2♦, a later cheap rebid serves as a second (“double”) negative, warning opener not to expect help.
Because game is already certain after 2♣, every bid below game can be used to describe the hand, which is exactly what a slam-going giant needs.
