Mock Up the Panel Spacing
Mock up the spacing on the wall in pencil so that you’ll see where to install each trim piece.
Install the Top Rail
To make as few cuts as possible, first mount the long upper horizontal piece, or rail, using glue and nails. If your existing baseboard doesn’t match the trim material, do the same for the bottom rail. Hold off on the middle rail for now.
Install the Stiles
With the top and bottom rails in place, install the stiles. Despite your measurements, go ahead and scribe each stile and cut with a handsaw to get a tight fit. If your panel spacing does not correspond with the wall’s studs, you can glue and nail each strip to the wall before proceeding to the next one.
Install the Middle Rail
Follow the same steps to mount the middle rail, which consists of five shorter pieces. Again, for the best fit, scribe each one and use a handsaw to cut before gluing and nailing. Let the glue dry over night.
Fill Nail Holes, Sand and Seal
Use joint compound to fill the nail holes, and sand the filled areas smooth. Seal each seam with paintable caulk. Wait a couple of hours (or overnight) for everything to dry. Wipe down the wall with a damp towel to remove sanding dust and debris.
Prime and Paint
Prime and paint the wall to achieve the desired shade. Two coats were applied on the MDF pieces and three coats on the formerly army-green drywall to get a creamy white.