Another binding jig question

My next big task is to build a binding jig along the lines in this link

http://www.dewguitars.com/BindingJig/Binding%20Jig.htm

A Ribbecke jig I think. The one point that isn't clear to me is the set up on the router base - specifically the delrin/plastic doughnut thing attached to the router base which is designed to ride on the instrument's back/top whilst cutting the binding channel. I've never used such a set up or anything remotely like it so if anyone had a good close up pic of this part I'd be forever grateful. An explanation of how it works and what I'd need to do to make this part would be superb as well. Not asking for much am I?!!

I think the rest looks reasonably easy to make and I'll be b*****ed if I'll pay what Stewmac or LMI are asking for their binding jigs.

Cheers

Gerry

Gerry

PM Ken Timms to explain it - he made one for me to fit my set-up that uses a laminate trimmr, bearing rebate cutter and deSoutter vertical pantograph. Much better than those home made things and the result of a chance stumbling across a giveaway eBay auction...

Here's a pic of my donut. I made out of UHMW plastic with a hole saw. Also John at Blues Creek guitars sells them for $15.

I think this is the thread we discussed way back http://www.ukuleleunderground.com/forum/showthread.php?28134-Cutting-binding&highlight=swivel

Thanks for the replies guys. Ken - PM sent.