This database contains approved defenses to methods permitted under the ACBL Mid-chart. When playing in an event governed by the ACBL Mid-Chart, you may refer, during the bidding and/or play, to any defense contained herein to a Mid-Chart method being used by your opponents (you may also refer to your own defensive method).

If you choose to play a method permitted by the Mid-Chart, you are required to:

  1. Pre-Alert the method prior to the start of the auction on the first board.
  2. Have a complete written description of the method available for your opponents.
  3. Except for those methods on the Mid-Chart designated by an asterisk (*), have a copy of an approved defense from this database available for your opponents should they wish to use it. If there is no approved defense for the method you wish to play, you may not use that method until such time as you have submitted a defense to ACBL and that defense has been approved (except for those methods designated by an asterisk (*) on the Mid-Chart, which do not require a suggested defense).

The intent of these requirements is to permit responsible pairs a reasonable amount of freedom to determine the methods they wish to play while insuring that no advantage is gained from a method that is unknown and/or whose submitted defense is inadequate.

Convention and Defense Approval

Approval Committee Members: Chip Martel, Jeff Meckstroth.

This sub-committee is also responsible for approving experimental methods to be added to the ACBL Mid-Chart and for approving defenses to Mid-Chart methods to add to the ACBL Defense Database. The committee is unlikely to approve requests for artificial openings that do not promise length in the suit bid or any weak openings for two-board segments.

All proposals must include:

  1. a complete description of the method, including responses and rebids and what happens in competition,
  2. a detailed defense including initial actions, responses to the initial actions (including in competition), actions after opening-P- bid/P (and responses there to), delayed actions such as opening-P-bid- P-P/bid

Submissions missing these details will not be approved.

Basic Concepts vs. Artificial Preempts

Direct double of a bid below 2NT shows 13-15 (balanced or semi-balanced) or a strong hand. Any other double which is your side’s first non-pass call is for takeout. After an overcall when their suit is unknown, bidding the cheaper minor is an artificial force (like a cuebid). If the preempt could be either strong or weak, assume the weak meaning.



A. Opening 4 of a minor showing an unspecified solid major
B. 2H opening which is 3-suited, short in diamonds
C. 2S opening which shows the minors
D. Transfer preempts (whether 1 or 2 under the suit bid)

E. Opening 2C showing weak diamonds or strong hand
F. 3-level preempt showing unknown solid suit
G. Opening 4NT showing strong minor suit
H. 2H opening which is weak with both majors (5-5)
I. 2D opening weak majors (5-4), known 5-card suit
J. 2H opening weak majors (5-4), known 5-card suit
K. 2H opening weak showing hearts and another suit


A. 2D opening weak majors (5-4)
B. 2H opening weak majors (5-4)
C. 2NT opening which is a weak preempt in a minor
D. 2D opening showing weak 2 in major with other strong meanings
E. 2S opening which is a preempt in a minor


A. 2C opening limited hand with major
B. 1H opening showing spades, limited