Forgot to include an example for you to look at how this works. Did a quick
search for "router collar" and this was the first of hundreds.....

http://www.ucc-udb.com/C21-C27pdf.PDF

A good source would be Lee Valley www.leevalley.com or Pat Warner
www.patwarner.com or many other places like Rockler, Highland Hardware
etc., etc....

Bob S.