Pat, Fifth photo from top, or second from bottom at
http://www.patwarner.com/t_square.html.

Being a router guru, I assume you used a router. Did you also use a
jig, like the Leigh, Akeda, or Porter-Cable?

I must confess, I have not read all the text on your web page so I
apologize if you describe how you did it somewhere and I was too lazy
to find it....