for filling nail holes
to seal gaps between molding and walls and ceiling
for adhering outside corners and returns
Modern crown molding can be traced to the late Renaissance, when designers adapted elements of Greek and Roman architecture to ornamental plaster and wood cornices used to disguise and beautify the juncture of ceiling and wall.
The cornice's curves, referred to by classical names such as scotia, cyma, and ovolo, add sculptural definition and visual interest to an otherwise characterless space. The molding used can be simple stock, like the single-piece crown installed here by This Old House general contractor Tom Silva, or elaborate pieces built up from separate lengths of various profiles.
Installing crown is only slightly more complicated than running baseboard. The variety of different joints and saw cuts, including a coped corner joint, an outside miter, a square cut, and a scarf joint, are best done with a coping saw and power miter saw. With practice, you should be able to make tight, long-lasting joints.