Opening Bid:   Two Clubs - 11-16 HCP

This is an opening bid that is frequently used 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.

Responding to an Opening Bid of Two Clubs
  • 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 she has a 4-card major
  • A response of 2NT is invitational.  Opener should pass with 11-13 and bid 3NT with 14-16 HCP
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 precisely 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 is forcing.  (An immediate jump to the 3-level in a major is only invitational.)

Negative Double by Opener
Negative doubles are almost always used by the responder in a competitive auction, but it can be used by either partner after an opening bid of 2.  If you are the opener, and your partner asks about a major by bidding 2, you might get an interference bid on your right.  If they overcall with a major, you can double, promising the other major.  If they overcall with a diamond bid, you can double to show both majors.  (With only one, you should just bid it.)  Partner is allowed to convert the negative double to penalty.

Gerber
A jump to 4 by responder may appear to be a jump raise, but it's Gerber, asking for keycards.  There are five key cards... four aces and the K, with only three kings.

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 5-5 in the minors, we use an opening bid of 3NT to show that hand.  Most other club systems prefer a 2NT call, but we use that bid to show both majors.    3NT Opening Bid