Miter joints are nice to look at, but the end grain surface doesn’t offer a lot of gluing strength. One way to reinforce the miter (and add a decorative touch) is to add keys that run across the joint. But cutting perfect slots for the keys isn’t always easy. You need to hold the assembled workpiece at 45° and then pass it over a table saw blade or router bit. The jig shown above makes it easy to cut slots for miter keys.
the jig consists of two plywood sides that hold a carriage. The carriage supports the box at the correct angle. The jig also has a replaceable hardboard backer that acts as a zero-clearance insert to support the cut and help prevent tearout.
To keep the workpiece stable during the cut, I added a toggle clamp fastened to an easily adjustable base. With this jig, the quality of the boxes I make has gone up. I get clean, accurate cuts every time.
