Steps:
- Use circular saw and clamped-in-place straightedge guide to cut window-box parts to size from medium-density overlay.
- Use drill/driver to drill counterbore and screw-pilot holes, then assemble the box parts with polyurethane glue and 2-inch-long ceramic-coated deck screws.
- Attach two galvanized-steel right-angle brackets to the house wall directly below a window. On vinyl siding, be sure to insert two small wood blocks behind each bracket to avoid crushing the siding.
- Drill pilot holes through the siding and secure each bracket to the house wall with 2-inch-long ceramic-coated deck screws.
- Drill six ⅜-inch-diameter weep holes through the bottom of the window box.
- Fill all screw holes with auto-body filler, then sand flush with random-orbit sander.
- Prime and paint the box with exterior-grade house paint.
- Set window box onto brackets and secure by driving ¾-inch galvanized or stainless steel screws up through the brackets and into the bottom of the box.