Many sills also extend slightly beyond the sides of the casing—but the design is really up to you. rout a decorative profile on the front cut notches in the rear of the stool. and sides of the stool plate. to fit around the window framing.. I would love to put casing around every window in my home. however, i have a couple of curved transom windows and chair rail in 3 rooms, in which, the chair rail runs from window to window, stopping at the edge of the windows. i’m not quite should how i would put the casing around either of those windows.. The final step for both the door and the window trim is building and installing the head casing assembly. it’s made up of three parts: the fillet, a 1x6 and the cap molding. traditionally this cap molding was solid, but since a solid molding this large is hard to come by, we substituted 2-1/4-in. crown molding..
