You may find that you want to treat the sides and top of a cased opening the same. So you'll take the same profile that's used on the sides, or jambs, and run that all around the opening. In this example, a cased opening is created by using the same trim on the sides and on the top of the doorway. In a window application, a "picture frame" effect is created by using the same profile all around (top, bottom and sides).