http://www.woodshopphotos.com/albums.../edgeguide.jpg

As promised, here's a drawing on an edge guide for the DW621. It could
be made for other routers, too. I just based the dimensions on the
DW621 since it was the router in question. I have an idea for a
different fence but haven't had time to draw it yet. It would make it
easier to track around the edge of a round table top for example.

The fence was designed to be removable and a handle could be installed
on the top giving an enlarged base for stability even when you don't
care about guiding on an edge.

It was designed to be made from readily accessible materials and should
be within the grasp of even the most basic woodworker.

Dimensions could be had upon request.

Dave