MultiLandy / Cappelletti

This convention can help you defend against a NT opening. It shows precisely the content of the overcaller's hand. It should not  be used with fewer points than required for a general Overcall. 

With Multilandy - 

2C = 5 cards in in one major and 4 in the other

2D = at least 5 cards in a major suit 

2H = 5 hearts and 5 in a minor

2S = 5 spades and 5 in a minor 

2NT = 5 cards in both minors 

Response to 2C overcall

Choose the preferred major. With good support raise to game in preferred major suit 

If no preference bid 2D to allow partner to choose

Response to 2D overcall 

Bid 2H. The overcaller can correct to spades 

Bid 2NT if you have support in H or S and Opening Points

Response to 2H overcall 

Pass or raise to 3 to invite a game contract or 4 to play.

Bid 2NT to ask partner to bid the minor suit

Bid 2S with no heart support and 6+ spades 

Response to 2S overcall 

Pass or raise to 3  to to invite a game contract or  4 to play 

Bid 2NT to ask partner to bid the minor suit

Bid 3H with no spade support and 6+ hearts

Response to 2NT overcall 

Choose the preferred minor 

NB.  The Cappelletti Convention is the same as MultiLandy with the 2C club and 2D bids reversed in meaning.