Old Fart Woodworking on youtube.
Kevin has been sending out some mitre boxes to folks and rather than leave them on their own to figure things out this seemed like a good way to start.
This first box was developed and then patented by Justus A Traut in June of 1877. In the video he has dismantled the box and walk through reassembling and setting it up.
There will be a few more videos added as time goes on.