Don't join rails much, but I have used both a straight edge and the method in the video (after taking a Festool class). Both work equally as well, regardless of other posts in this thread. There is some logic in it since your saw is what is riding on the rails and, if your saw, is set up to run true on the rail, then it should line the rails up when joining them. I agree, though, it really isn't faster than using a straight edge and both do get the same result, both in class and in my shop.