Two lifting daggerboards

Sailboats with two lifting daggerboards are generally sailing catamarans. 
However, some monohull sailboats can be fitted with them.

The daggerboards are fully retracted into the daggerboard wells, giving the boat a very shallow draft with the daggerboard up.
Adjusting the daggerboards improves and optimizes course stability on downwind points of sail.
Using the daggerboards in the low position enhances the catamaran's upwind performance.