Measure the walls to determine the height and width of the panels. Whether you are running the panels beneath a chair rail, as here, or at full wall height, space the panels at least 3" to 4" below the top point and above the baseboard. Panels should be spaced 2½" to 3½" apart. Molding used can be a standard width (2¼"), or a thinner profile for a more delicate look (shown here).
Measure a reference line to mark the panel’s top and bottom. Then mark off each panel’s four corners with tape. Make sure the lines are level. Use a miter saw set at a 45-degree angle to cut the molding at the height and width needed for your panels, then paint these pieces and let them dry.
To install, run a bead of construction adhesive along the back of the molding. Align the top corner of the miter cut with your reference mark for the panel; remove the tape and press the molding against the wall until it sets up. Wipe away any excess glue with a rag. Repeat with the adjoining piece, fitting the mitered edges. After the panel is placed, further secure the molding with finish nails, starting an inch past the miter. Fill any nail holes with putty and, if needed, touch up the paint.