Cappelletti is a convention usually attributed to Mike Cappelletti and his longtime partner Edwin Lewis, but origin of the concept is also claimed by Fred Hamilton, John Pottage and Gerald Helms. Alternative names include "Capp", "Hamilton" and "Pottage". It is designed to allow any one- or major two-suited overcall of a 1NT opening. It is one of many conventions for interfering over opponents' 1NT opening. This convention is alertable.
After left-hand opponent or right-hand opponent opens 1NT, and passes,
- Double is a penalty double. Per partnership agreement, generally 15-17 pts or 16-18 pts. Stronger the opponent 1NT opening is, stronger the doubler hand is required.
- Partner usually pass, or (rarely) escape to his/her long suit with a very weak hand.
- 2♣ shows one-suited hand (usually, 6 or more cards). The partner is supposed to:
- 2♦ shows both majors (at least 5-4).
- Partner will pick a suit with weak hand, or bid 2NT as invitation of majors.