MECWELL CONVENTION AFTER OPPONENT OPEN 1NT
Used by the Americans Champions Jeff Mechstroth and Eric Rodwell
it is applyied in two conventios: one against weak nt (12-14 hcp)
and the other against strong nt (15-17 hcp).

One caracteristic of this convention is to show only one suit major
bidding overcall in 2 or 2.

Part 1 - against strong nt
Opener  Overcaller
   1nt        ?
              double => is a relay to 2 and shows a single minor or both
                               majors, then after his partner (advancer) bid 2:
                                - overcaller pass with long Clubs suit;
                                - overcaller bids 2 with long Diamonds suit;
                                - overcaller bids 2 with both majors.
              2 => means 5 and a major;
              2 => means 5 and a major;
              2 => natural 5+ cards;
              2 => natural 5+ cards;
             2nt => both minors 5+ 5+ cards.

Part 2 - against weak nt
Opener  Overcaller
  1nt         ?
             double => 14+ hcp
                2 => 2 black suits or both majors
                2 => 5+ cards and a major
                2 => natural 5+ cards
                2 => natural 5+ cards
               2nt => strong hand with both majors
                3 => 5+ cards and 5+ cards

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