Opening Bid:   Two Clubs

This is a frequently used bid in all strong club systems...  It shows an opening hand with a club suit.  Players often modify it with different agreements, but the most common way of playing it is to have 11-16 HCP, and at least a 5-card club suit.  Some players prefer to promise a 6-card suit but that agreement restricts the use of the bid.  The opener may have a 4-card major.

Four Diamonds - Five Clubs
With four diamonds and five clubs, opener should start with a 1 call and then rebid 2.

Five Diamonds - Five Clubs
With five diamonds and five clubs, strong club systems use an opening bid of 2NT to show both minors.

Responding to an Opening Two Club Call
  • A response of 2 or 2 is natural and non-forcing
  • A response of 3 or 3 is natural and invitational
  • A response of 2 is artificial and asks opener if he has a 4-card major
Opener's Rebids After a 2 Asking Bid by Responder:
  • 2 or 2 shows a 4-card suit
  • 2NT denies both a 6-card club and a second 4-card suit.. The pattern is 5332
Responder Rebids Either 3 or 3 After Asking With 2
If responder uses the 2 asking bid and then rebids a major at the 3-level, the bid is natural with at least a 5-card suit and forcing.

Negative Double by Opener
This is about the only place I can think of where the opener gets to use a negative double in a competitive auction...  Suppose the opener bids 2 and responder asks about a 4-card major by bidding 2.   then, suppose the next hand overcalls with a suit, for example by bidding 2, and opener has a 4-card heart suit...  Seems like a perfect spot for the opener to double.