"Runnin' crown" is a term used by carpenters when they are installing a head mold of some type on top of cabinets or in any room. There are several type of ceiling-to-wall moldings one can use; crown, cove, bed, picture and flat moldings to name a few. After you decide what style you want, then you decide what size to use. We usually combine a few different sizes and styles on top of a cabinet. In this case we are "running" a two piece. The lower trim is a flat piece with a "bead' and the top piece is a 3 1/4" crown. It really 'dresses up" the cabinets. In this photo, Tom is filling the nail holes.