The miter jig clamps to the crosscut sled to make accurate 45° cuts. Then it's quick to remove to use the crosscut sled for straight cuts. This jig is also versatile enough to be used by itself by running it against the table saw rip fence to make mitered cuts. Making a miter cut using the jig is simple. Just clamp it to the back fence of the crosscut sled as shown here. Make sure the jig lines up with the kerf line of the sled. (The jig can be placed on either side of the saw kerf.) Set a workpiece against the clamp support and lock it in place using a toggle clamp. Now just push the crosscut sled forward to make the cut on your workpiece.
To build the miter jig, start by cutting the hardboard base and the plywood clamp support to final size. Use a combination square to lay out the angles on the front edge. Taking extra care to lay out and cut these edges will ensure the accuracy of the jig. The base and clamp support are then held together with glue. The fence is cut from solid stock and is attached with screws through the bottom of the base and clamp support.