Derek Cohen (in Perth, Australia)
The jig essentially consists of a method of trapping the plunge router to travel in the direction desired, along with a set of clamps to hold the work piece. The advantage of this design is that it is set up very quickly and is very reliable. The track is to set up stops.
The idea came from Fine Woodworking magazine. My only modification was to change the clamping system. The Matchfit clamps (by Microjig) slide into dovetails. These are more flexible and adjustable than the clamp on the FWW model
My version ...
I briefly owned a mortice machine, and quickly sold it. This router-based jig is far easier to maintain (than sharpening augers). Since it works from above the workpiece, it is easy to work accurately. All very intuitive.
Regards from Perth