MULTIPLE MEANINGS of a DOUBLE


CONTEXT DETERMINES THE ACTUAL NATURE OF DOUBLE

2ND POSITION....A CLASSIC TAKE-OUT DOUBLE (*)

Either 12-15 with ideally shows support for all unbid suits save the lowest unbid minor suit that may be just 2 cards.
Or        16+ any hand  
Don't use a T-O double with just 2 suits and 12-15 - bid the longer suit and rebid the in the other if it makes sense to do so showing 5-4 at least. With a single suited hand  show your suit and make a simple rebid it if weak showing 6+ cards.
See T-O Double for responses
If holding any 5-5 or better there are special overcalls available see 55+

PROTECTIVE  POSITION

DOUBLE DENIES HOLDING 2  4+CARD  UNBID SUITS AND ASKS PARTNER TO PICK A SUIT
"PROTECTIVE BIDDING PROCEEDS UNDER THE SUPPOSITION OF A NEAR 20-20 POINT SITUATION"
See protective bidding for more details

WHERE A CONVENTIONAL RESPONSE BID IS PRESCRIBED

In 2C sequences following  intervention  Double is used to indicate the 2nd step
In 2D sequences the responder  uses  * whenever a 2N bid would have been made without  intervention
In 5-5 sequences  * codes for step 2 (PASS for step 1) following a 3|4N inquiry
In 4N Blackwood  * codes for 1|3 Keycards (PASS for 0|2|4 KCs)
In 1C|D opening sequences * codes for a the other Major suit & promises (7)8+ HCP

NEGATIVE DOUBLE  1X(p)-1|2Yno-jump(opp)-* or 1X(p)-weak_jump_o'call-*

BETA does not employ this double in the old  'SPUTNIK' style (specifically targetting the highest unbid Major) - we use as in the original intention of negative double: to show certain values [(7)8+ @ 1-level, (9)10+ @ 2-level, (11)12+ @ 3-level] AND  to suggest to partner  interest in  ALL unbid suits.
It does not DENY|SHOW interest in partner's opening bid suit - essentially it provides a FREE bid opportunity to his partner. Note: BETA never uses DOUBLE to either show or deny support for partner's suit ... BETA considers this approach to be far too limiting on the usefulness of this most economical bid.

DOUBLE in a non-forcing situation, where both sides have an agreed suit is COMPETITIVE

Partner can decide to bid higher or PASS (territory where Jules Verne's LAW of TOTAL tricks applies) with full attention to vulnerabilities.

DOUBLE at the 3-level in a competitive & forcing situation

Asks partner to cue-bid a feature in an unbid suit OR to show support for any of doubler's declared suit OR bid 3N as appropriate - but NOT to PASS! - Importantly it never declares any interest in your suit - rebidding your suit only if it can stand alone!

DOUBLE at the 4 level must be made with due care

While hinting a desire to further develop the bidding, which partner must accede to when holding further unannounced key information|values, BUT doubler must also be fully  aware that partner is entitled to PASS: converting the double to penalties. As this is very likely to occur if  the responder has PREVIOUSLY PASSED.  
Also partner's double is NEVER asking you about your suit - its entirely up to your partner to show support for your suit at this level -  your choice will be just between partner's declared suits!

Final warning do think thrice about forcing partner at this level with a double - IF he has previously PASSED. Partner is likely to PASS again unless he has still more to give!

In cue-bidding sequences a DOUBLE

At any level, 2-5, following intervention shows a shortage or control, 1st or 2nd round control in the opponents bid suit. This double come cue-bid  is strictly NOT for penalties!

DOUBLE of an opponents conventional bid e.g. a TRANSFER bid

Shows holding of hitherto undeclared either LENGTH or HIGH CARDS in that suit. E.g  Transfer bids or a 2C Stayman etc.