The Rosenkranz Double is used when your LHO (left-hand opponent) opens the bidding, partner makes an overcall, and RHO (right-hand opponent) also bids. A double is artificial, showing 3-card support for partner’s suit with at least one of the top three honors.

    K73
    83
    KQ93
    T873
  West
1
North
1
East
2
South
Double 1

(1) Rosenkranz double, showing 3-card spade support with a top spade honor.

In contrast, a simple raise of partner’s suit denies a top honor in that suit. For example:

    9873
    AK5
    JT9
    965
  West
1
North
1
East
2
South
2 1

(1) Rosenkranz, showing a 3-card diamond raise without a top diamond honor.

Rosenkranz doubles are used through the 2-level. The choice must exist to either (re)double or raise partner’s suit to the 2-level.

Both the direct raise and the double show 6-10 points. A stronger hand with support must cuebid instead to show 10+ points.

The Rosenkranz double is named for inventor George Rosenkranz, a preeminent Mexican expert. The purpose of the convention is to help partner on defense should the opponents win the auction.

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