Which of the following best describes a cornice?

A cornice is best described as a decorative box that covers curtain hardware. This architectural detail serves both functional and aesthetic purposes in window treatments. By concealing the drapery rods or mounting hardware, a cornice creates a clean and polished look, enhancing the overall interior design of a space.

Cornices can be made from a variety of materials and may be upholstered in fabric or covered in decorative paper or paint to match the room's decor. Their structural form can also add depth and interest to windows, making them not just a practical element, but also an impactful design feature.

The other descriptions do not accurately capture what a cornice is. For instance, a type of roman shade refers specifically to a style of window covering that folds up as it is raised, which is distinct from the decorative function of a cornice. Similarly, a soft fabric used for drapery lining and a sheer fabric intended for windows serve different purposes in terms of light diffusion and privacy, not addressing the decorative and concealment aspect that a cornice provides.