how to install vinyl exterior window sill
1. Unscrew and remove the storm window from the outside of the window. 2. Pry off the vinyl siding and J-channel from around the perimeter of the window. 3. Use tin snips to trim off the metal flashing covering the exterior windowsill. 4. Notch the vinyl windowsill with tin snips to fit the existing windowsill. 5. Nail the vinyl windowsill to the old wooden windowsill. 6. Glue a vinyl end cap onto each end of the vinyl windowsill. 7. Set vinyl casing against vertical side of window and scribe bottom end to match angle of sill. 8. Cut bottom end of casing with aviation snips, then install the casing against the window.