Gluing and clamping a single miter joint can be a challenge. It’s often hard to get the joint lined up and then hold everything in place until the glue dries. To make this task easier, I built the clamping jig you see here.
The jig consists of a large plywood base to support the pieces to be joined. A pair of triangular-shaped blocks have a tongue at the bottom that slides in a groove in the base cleat to hold the pieces from the side. Sandpaper attached to one edge keeps the workpiece from slipping. A third triangular block travels on a T-track so it can be locked in place to secure the joint from the top. Before assembling the jig, I waxed all surfaces to prevent any glue from sticking to the parts.
To use the clamping jig, apply glue to the mitered ends. Now you can lay the two pieces on the base with the mitered edges pointing toward the bottom edge of the jig. Be sure to carefully center these pieces on the T-track. Next, slide the inside clamping block against the workpieces and tighten the knob. Then move the outside clamping blocks into position and clamp them in place with a bar clamp. For maximum pressure, position the bar clamp near the base of the clamping blocks. Now just let the jig hold the pieces in place until the glue dries.
