Cappelletti (aka Hamilton)

This convention is known by two names because Mike Cappelletti and Fred Hamilton are both credited for it. For simplicity I am just going to refer to it as Cappelletti.

Cappelletti is a defensive bidding convention for use after an opponent has opened 1NT. Overcaller's available conventional calls are as follows.

Overcall	Meaning
Double	Penalty (See also: Gates Double)
2	A one-suited hand (any suit, 5+ cards) with roughly 11-15 points.
2	At least 5-4 or 4-5 in hearts and spades, asks partner to correct to either major.
2	At least 5-5 in hearts and a minor.
2	At least 5-5 in spades and a minor.
2NT	At least 5-5 in clubs and diamonds.

Response	Meaning
Pass	Shows 6+ clubs.
2	An artificial bid, asking partner to pass if his suit is diamonds or to bid 2/2/3 depending on which suit he has.
2	Shows 6+ hearts, nonforcing.
2	Shows 6+ spades, nonforcing.

Response	Meaning
Pass	Shows 6+ diamonds.
2	Natural preference, nonforcing.
2	Natural preference, nonforcing.
2NT	Natural, invitational. Shows about 11-13 points, balanced.

Response	Meaning
Pass	A weak hand with tolerance for hearts.
2	Promises 6+ spades, no heart support, nonforcing.
2NT	Artificial, no heart support, asking for partner to bid his minor suit at the three level.
3	Promises 6+ good clubs, no heart support, nonforcing.
3	Promises 6+ good diamonds, no heart support, nonforcing.
3	Promises 3+ hearts, invitational.
3	Promises 6+ good spades, invitational to 4.
3NT	To play.
4	To play.
4	To play.

Response	Meaning
Pass	A weak hand with tolerance for spades.
2NT	Artificial, no spade support, asking for partner to bid his minor suit at the three level.
3	Shows 6+ good clubs, no spade support, nonforcing.
3	Shows 6+ good diamonds, no spade support, nonforcing.
3	Shows 6+ good hearts, no spade support, nonforcing.
3	Promises 3+ spades, invitational.

Response	Meaning
3	A weak hand with tolerance for clubs.
3	A weak hand with tolerance for diamonds. Tends to deny club support.
3	Shows 6+ good hearts, no support for either minor, nonforcing.
3	Shows 6+ good spades, no support for either minor, nonforcing.
3NT	To play.
4	Shows 3+ clubs, invitational.
4	Shows 3+ diamonds, invitational.
4	To play.
4	To play.

Mike Cappelletti and Fred Hamilton, both American experts, are credited for this convention. See also Multi-Landy, which is very similar but reverses the meanings of the 2 and 2 overcalls.