If your friend wants you to help repair the cornice on his house, you’d better bring a ladder. The cornice is the decorative molding that stretches horizontally along the top of some buildings.
The cornice that you see on some buildings serves as a decorative element and also functions as a way to keep rainwater from dripping down the walls. The cornice juts away from the building enough that the rainwater flows away from the building. Not just for buildings, the word cornice can also describe raised decorative molding right under the ceiling in a room or a similar decorative topping that crowns some windows to hide curtain rods.