Cappelletti in using for the opening of 1NT owning 1 suited and 2 suited hand.

as follows:
2C Owning a one-suited hand
2D Owning both majors
2H Owning hearts and a minor
2S Owning spades and a minor

To 2C bid, partner "relays" to 2D to pass if the suit is diamonds
To 2H or 2S, partner pass or bid 2NT to permit the overcaller to bid Club / Diamond.

Landy : for the defence of for opener 1 NT by opponent
2 C : having 4 + 4 or better in major colour and have 13 Up HCP
If you play landy, other overcalll for 1 NT is natural