The Woodgrain Millwork 11/16 x 2-1/2 x 96". Solid Pine WM 1099 Window Stool is an interior moulding that serves as a sash or window frame sill cap. This Solid Pine WM 1099 Window Sill can be used to rejuvenate your existing windows with minimum work. Window stool is the finishing touch for any style window. This pattern also eases the transition from window frame to wall.