What's the Lavinthal Discard System ?
Lavinthal Discard SystemWith this agreement, the first discard you make shows your suit preference.
You do not like the suit led and you do not like the discarded suit.
Your signal tells partner which of the two outstanding suits you prefer.
A high card signals your interest in the higher ranking of the remaining suits - a low card for the lower ranking suit. This is known as Lavinthal in the US, or as McKenney in the UK.