Principle

What do we do with an opening (12-15HP) and a 5+card in the suit of the enemy opener? PASS! Partner will double protectively as of 8+HP and with 2+card in enemy suit.

Also included is a discussion of the possible interpretations of a double (protective, informative, distributive).

Doubles

X in 1st round

2nd pos = Infodouble

4th pos = Protective Double

in 2nd round

2nd pos = Sandwich, 12-15(17)HP, 5+card previous enemy suit, negative other enemy suit

4th pos = distributive remaining suits, 8-11HP

in 3rd round = distributive (44) remaining suits, 8-11HP

Sandwich

Sandwich X

X promises 12-15(17)HP, 5+card in suit of the enemy in the position just before you, AND

1) enemy has bid 2 suits: also 3+3+ in remaining suits

2) enemy has bid 3 suits: 4- in last remaining suit

remark:

• after 3 enemy suits: X = exactly 4-cards remaining suit, 12-15HP. Because a 5+ in another suit and 12-15HP would have been a normal bid in 1st round. As of 16+HP we do an informative double anyway.
• a sandwich double is only possible in 2nd position. In 4th position it's always negative.
• extra requirement (3+3+ of 4+ in remaining suit) makes sure that partner can escape to a playable contract if he doesn't want to reconvert the double or play in the enemy's suit: he can simply bid his lowest suit en be sure of a 4+3+ fit.
  

Further Bidding

#1: Opening suit without further competition: sandwich by protective double

/(1♣) - PASS - (PASS) - X: protective, 8+, 2-3(4)♣

/(PASS)

- PASS: sandwich, 12-15HP, 5+♣

- bid: no sandwich

#2: Opening suit (2nd man in 2nd position): sandwich by double in 2nd hand

/(1♣) - PASS = possibly sandwich - (1♦) - PASS

/(1SA2♣) = not outside opening suit; so 2 suits remaining

- X = sandwich, 12-15HP, 5+♣, neg ♦ (so 3+♥ 3+♠)

- (PASS)

- PASS = (1)2+♣

- 2♥♠ = weak

- 2♦ = cuebid, strong, ask for stops (use enemy's other suit)

/(1♥) = outside opening suit

- X = sandwich, 12-15HP, 5+♣, neg 0(2)♥ (so (3)4-♠)

- PASS = possibly still a 5+♣ and 4-♥, hope for partner's double

/(1♠) = outside opening suit

- X = sandwich, 12-15HP, 5+♣, neg 0(2)♠ (so(3)4-♥)

- PASS = possibly still a 5+♣ and 4-♠, hope for partner's double

/(2♦) = outside opening suit, fit with answerer's suit

- X = sandwich, 12-15HP, 5+♣, neg 0(2)♦ (so 4-3+♥♠)

- PASS = possibly still a 5+♣ and 4-♦, hope for partner's double

#3: Answerer's suit (4th man in 2nd position): sandwich double in 4th hand

/(1♣) - PASS - (1♦) - PASS = possibly sandwich

/(1SA2♣) = old suit - PAS

- (2♦SA)

- X = sandwich, 12-15HP, 5+♦, neg ♣ (so 3+♥ 3+♠)

/(1♥) = new suit - PAS

- (1SA of 2♦) = repeat of suit first answer

- X = sandwich, 12-15HP, 5+♦

- (2♥) = fit 2nd suit opener

- X = sandwich, 12-15HP, 5+♦, 0-3♥

#4: In 4th position (2nd man OR 4th man): distributive double

/(1♣) - PASS - (1♦) - PAS

/(PASS)

- X= distributive, 8-11HP, neg ♣♦ (dus ♥♠)

/(1SA) - PASS - (PASS)

- X= distributive, 8-11HP, neg ♣♦ (dus ♥♠)

caution! sandwich double on answerer's suit is impossible in 4th position

Distributive X and delayed following bids

1) 8-11HP and 44 in remaining suits, distributive

- 1st method: X in 3rd round (see Doubles)

- 2nd method: X in 4the (protective) position (see Doubles and Sandwich #4)

- 3rd method: 10-11HP, cuebid in lowest enemy colour

2) 7-11HP and weak long suit: delayed following bid

(1♣) - PASS - (1♦) - PASS / (1SA or 2♣♦) - 2♥♠ = 5+♥♠ with 1 honor card, 7-11HP

if we wouldn't be playing sandwich defense, we could use a normal X in the 2nd round for distribution.

Examples

/(1♦) - PASS - (1♠) - PAS

in 2nd round:

/ (1SA)

- 2♦: cuebid, dist, 8-11HP, 4-♣4-♥

- 2♣♠: 8-11HP, weak 5+♣♠

- X: 12-15(17)HP, 5+♦, neg ♠ = sandwich on opening suit

- PASS = possibly still sandwich 5+♦, 4-♠

- (PASS)

- X: 8-9HP, 4-♣4-♥

- 2♦: cuebid, dist, 10-11HP, 4-♣4-♥ = cuebid is stronger than an X for dist

-2♣♠: 8-11HP, weak 5+♣♠

- (2♦♥♠)

- X: 12-15(17)HP, 5+♠, neg ♦ = sandwich on answerer's suit

- PASS = possibly still sandwich 5+♠, 4-♦

/ (2♣♦♠)

- X: 12-15(17)HP, 5+♦, neg ♠ = sandwich on opening suit

- PASS = possibly still sandwich 5+♦, 4-♠

/ (2♣♦) - PASS - (2♥♠)

- X: 12-15(17)HP, 5+♠, neg ♦ = sandwich on answerer's suit

- PASS = possibly still sandwich 5+♠, 4-♦

in the 3rd round:

/ (1SA) - PASS - (2♦) - PAS

/ (PASS)

- X: 8-11HP, 4-♣ 4-♥

- 2♣♥: 8-9HP, weak 5+krt ♣♥

/ (2♠) - PASS - (PASS)

- X: 8-11HP, 4-♣ 4-♥

- 3♣♥: 8-11HP, weak 5+krt ♣♥