So this isn’t a joint that you are going to use every day. It’s basically for larger projects when you want a really strong joint. Also, when you have a project like a table, where you have long legs, sometimes there can be a lot of twisting force on table top. That could be a good time to use a double mortise and tenon joint. I like the way he cleans it off with the chisels. If you don’t do that your joints won’t be as strong as they need to be. Every shop needs a good set of chisels.