How to Connect Mitered Frame Joints

Build a miter framing jig for quick and accurate miter joint installation. Place one sheet of 3/4-inch plywood flat on saw horses. Place three saw horses beneath the plywood, spaced evenly, to fully support the plywood and to prevent it from sagging.

Attach two 4-foot sticks of 2-by-4 lumber to the plywood in a 90 degree angle. Lay the lumber flat. Place a framing square against the outside of the lumber and align the lumber with the framing square.

Attach the lumber to the center of the plywood with 3-inch wood screws. Recheck the lumber with the framing square after you have inserted the screws to ensure proper 90 degree alignment.

Place your miter joints onto the plywood, using the lumber as a template. Slide the joints together until they meet into a 90 degree angle. Observe the joint of the miter and look for gaps or misalignment. The tips of the miter joints must align, as well as the inside corner of the miter.

Adjust the miter if it does not align against the template. Place the miter on a miter saw at 45 degrees. Trim the miter joint slightly, taking only a small amount off of the tip.

Realign the miter and check that the joint is tight. Place glue on each miter joint and slide the joint together and tight against the template built earlier. Attach the corner with a brad and nailer, which is only temporary until the glue dries.

Allow the glue to dry for 30 minutes before removing the miter joints from the template.