Cornices are a box treatment, usually constructed of wood that is padded and upholstered. Cornices can be as plain as a simple box over a window or feature a shaped top and/or bottom. Cornices can be embellished with trim or contrasting fabric. They are a great choice if using expensive fabrics because they require a fraction of the yardage needed for other window treatments. Cornices are a great way to hide blind and shade hardware.