The origin of this modification of the convention is unknown. The features behind the concept of this variation are employed after a No Trump opening by an opponent. Whether or not the concept can / should be employed only in the immediate seat or also as a balancing action is dependent on the partnership agreement.
The following outlines the meanings of these overcalls. Source is: David Stevenson.
Double: Any double is for penalty. Partner must pass.
Promises a balanced holding with 12-14 high card points and at least a 3-card Club suit.
Promises generally a 6-card plus Diamond suit. Natural.
Promises generally a 6-card plus Heart suit. Natural.
Promises generally a 6-card plus Spade suit. Natural 2 NT: Per partnership agreement. 3 : Promises generally a 6-card plus Club suit.
The overcalls employed in the Roche Defense conventional method are, for the most part, natural bids showing a one-suited holding instead of a two-suited holding. The individual partnership may alter this concept to meet the needs of particular bidding systems or as an adaptation to the partnership understanding. The partnership may also employ this method by any No Trump range with values adjusted accordingly.
Note: Some partnerships have agreed that the distribution of the holding, when overcalling could / may be reduced to 4-4 in both Major suits regardless of the state of vulnerability, otherwise the distribution is generally 5-4, 4-5, or 5-5 depending on the state of vulnerability. This is entirely a partnership agreement in all employed variations of the concept.
Since there are several idle bids available, the partnership can untilize them for other shapes, patterns, and distributions. Any jump response by the Advancer can / may constitute strength and length, but this again is an individual partnership understanding.
If you wish to include this feature, or any other feature, of the game of bridge in your partnership agreement, then please make certain that the concept is understood by both partners. Be aware whether or not the feature is alertable or not and whether an announcement should or must be made. Check with the governing body and/or the bridge district and/or the bridge unit prior to the game to establish the guidelines applied. Please include the particular feature on your convention card in order that your opponents are also aware of this feature during the bidding process, since this information must be made known to them according to the Laws of Duplicate Contract Bridge. We do not always include the procedure regarding Alerts and/or Announcements, since these regulations are changed and revised during time by the governing body. It is our intention only to present the information as concisely and as accurately as possible.
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