Cappelletti is used when the opponents open 1NT.

Aside from the Double in Capp -- the main purpose is to interfere with the bidding.
A Double is for Penalty -- only if your partner is exceptionally weak would he remove the double.
A Bid of 2C shows a one-suited hand -- this will relay to 2D and partner will show his suit at his next turn.
A Bid of 2D shows both Majors (at least 5/4) -- Partner will bid his best Major.
A Bid of 2H shows Hearts and a Minor Suit -- 2nt ASKS for the Minor.
A Bid of 2S shows Spades and a Minor Suit -- 2nt ASKS for the Minor.
A Bid of 2NT shows both Minors and asks for a T/O in the Minors.

Hand 1

Partner	K7 A652 KJ954 75
643 Q93 Q862 JT9		A95 KJT4 AT3 A84
	QJT82 87 7 KQ632

North	East	South	West
Pass	1nt	2S	Pass
2nt*	Pass	3C	Pass
3S	Pass	Pass	Pass

East openes a Strong Notrump.

South bids 2S* showing the Spade suit and a unspecified Minor. This partnership has agreed to play Cappelleti.

When it comes around to North
he bids an artificial 2nt* since he wishes to know his partner's Minor suit. He has an invitational hand and wishes to explore a possible diamond fit. When South shows Clubs North takes a preference for Spades and his partner passes.

Hand 2

Partner	7532 4 876 65432
98 AKT32 KJT32 A		Q64 J765 5 KQT97
	AKJT Q98 AQ94 J8

North	East	South	West
-	-	1nt	2H
Pass	3H	Pass	4H
Pass	Pass	Pass	-

South openes a Strong Notrump.

West bids 2H* -- showing Hearts and a Minor suit. This Partnership has agreed to play Cappelletti. When it comes around to East he raises Hearts to the 3 Level showing good support.

With a nice distributional hand and some encouragement from his partner West bids a game in Hearts.

Bridgeguy's Web Site ACBL Part 1 ACBL - Part 2 Capp Quiz