When the opening bid is 1 No Trump by partner, followed immediately by an overcall by the competing opponent, the partnership must have a defense method against such defense methods. The attempt is made to list such defense methods as guidelines for any continuances.

In the game of bridge two sides compete for the contract and it is this competitive spirit, which may confuse one partnership in order that this partnership does not reach the maximum contract, or convince the partnership to defend.

Such methods are not written in stone and they can very from partnership to partnership. However, these guidelines, these conventional methods have become part of the working partnership agreement of two players. The bridge player should acquaint himself with such methods in order to understand the concept, the idea, and form a general plan and strategy to combat such interference.

Halmic Defense to 1 No Trump Doubled
The origin of this conventional method is unknown. It is an escape mechanism after an opponent doubles your partner's 1 No Trump opening bid. The range of the No Trump is an individual agreement and the escape mechanism must be adjusted accordingly. This is a write-up in .pdf file format and will be automatically opened by the browser.

lebensohl Convention
The concept behind lebensohl is the result, or the solution of the following difficulty in bidding after an immediate overcall once partner has opened the auction with 1 No Trump. The lebensohl convention allows the partnership to employ continuances in order to reach the best contract.

Rubinsohl
This is a conventional method used by the responder and employed immediately after a competitive overcall. This conventional method uses the combination of transfers and lebensohl in competitive auctions, aimed at allowing a player to show his distribution with both weak and strong hands. This method was introduced by Mr. Bruce Neill of Australia in The Bridge World in the issue of May 1983, Volume 54, Number 8. The concept was based on the articles published in the same magazine by Mr. Jeff Rubens, who used the term Rubensohl.

Rumpelsohl Convention
Devised and developed by both Mr. Paul van Rijckevorsel and Mr. Hendrik (Henk or Henry) M. S. Willemsens of Utrecht, The Netherlands. They believed that a combination of both the lebensohl conventional method and the Rubinsohl conventional method would achieve the result that the partnership could possibly show more hand types than with either conventional method separately.

Maltais Convention
This conventional method was devised and developed by Mr. Raoul Maltais of Kenogami, Quebec, Canada. The concept is also known as and designated as Stayman After Overcall. The partnership agreement is such that if the immediate opponent does not interfere or compete following a No Trump opening by partner, then the Stayman conventional method is employed in order to discover whether the No Trump bidder holds a 4-card Major suit and the responses are identical to the Stayman convention. If the immediate opponent, however, interferes or overcalls, then the partnership initiates the Maltais conventional method to counter this interference.