BiltBest casement window sill stop – wood cover housing – OEM replacement part for BiltBest casement windows. This is referred to as the “inside stop” piece. These sill stops are held on with trim nails or screws and are either painted or stained by homeowners. They come to you as unfinished a-grade wood and we suggest you seal all sides. Take care when removing old units that may be held by old caulking, varnish or paint. We suggest you break the “seal” with a clean razor. Largest sizes available as standard are for 27 1/8″ inside visible glass sash size.