Normally a mitre joint (miter in US) would be considered ascetically pleasing, rather than being a strong woodworking joint.
But by inserting splines in the mitre joint, it becomes a very strong joint. These splines are running at 90 degrees to the mitre cut, and they have a large gluing area, thus giving them all this strength
The video below will show you how to make this simple jig, so you can make splines on your mitres in seconds. If you like the video, please consider subscribing to Irish Chippy channel
