I an not a big fan of Paul Sellars, but he does have some good ideas.  One of
his good ideas is a little jig made form scrap to guide his chisel when making
tenons and mortic(s)es.  He has a video on tenoned miter joints, much like they
have on wooden stretchers for canvas that come KD.  One of the bad things on his
site is no search function, so you have to go to youtube

https://www.youtube.com/watch?v=EM0NcKZNFfM



Ed Minch