a) crown molding
Angles out from wall at top of window, adding dimension lacking in flat stock. Together with frieze board and cap, makes up entablature, a feature found in classical house styles, such as Georgian, Federal, and Greek Revival.
b) mitered return
Covers end grain as it carries profile to wall.
c) frieze board
Serves as base for attaching crown molding and cap. Its ends line up with outside edges of casing.