They are beautiful and hefty, but marble boards are not meant for cutting — they will dull a good knife after a few strokes. They do have a place in the summer kitchen, though: Place a baking sheet or a roasting pan on the marble, fill it with ice, and leave it there for a half hour. The marble will become thoroughly chilled and can then serve as a natural refrigerator for sliced fruit and cheese that must sit out at a party or a dinner on a warm night.