Suction is a (restricted) defense against 1NT that does not promise an anchor suit. Each suited overcall shows the next-higher suit OR the other two suits. The suits "wrap" so that 2
may show clubs, for example.
Double and 2NT are used to show non-touching two-suiters.
||Clubs + hearts
||Diamonds OR hearts + spades
||Hearts OR spades + clubs
||Spades OR clubs + diamonds
||Clubs OR diamonds + hearts
||Diamonds + spades
Overcaller should have a good 5+ card suit at the 2-level, or a 6+ card suit if forcing the bidding to the 3-level. Similarly, overcaller should have at least 5-5 length with any two-suiter that requires partner to bid at the 3-level.
In response to Suction, advancer usually assumes a one-suited hand, and bids that suit. If overcaller has only shown a two-suiter (i.e. Double or 2NT), then advancer usually takes a preference in either suit. Any other bid by advancer is natural.
The benefits of Suction:
- Suction provides a way for all one-suiters and two-suiters to be shown.
- Suction can cause headaches for the opponents. What does a double mean? A cue-bid?
The problems with Suction:
- Unlike other defenses to 1NT, certain hands can't be shown at the 2-level, e.g. a club one-suiter or a minor two-suiter
- Suction is not permitted under the ACBL General Convention Chart (GCC), which says that two-suited overcalls must show "at least 5-4 distribution in two known suits."