Router edge guide and fluting guide
The basic idea can be used to make guides of different sizes. This particular one is quite large. The design makes a good edge guide, angle guide, and (in this size) fluting guide. You can see from its condition that it is used a lot. I glued a strip of Formica onto the work contact edge to enhance durability.
This is one of the largest I've made. A quarter circle of plexi, a scrap of wood, a couple of bolts, wing nuts and washers.
The clamp works very well. Leave some gap between the pieces.
A guide this size is not as convenient as an edge guide, but does work. I have three of different sizes, the smallest just big enough to accomodate the router.
The big ones do work well as angle guides. Note that the router is there for demonstration purposes. In use I would install a square base on the router.
With a 15" radius quarter circle this version reaches 10" (center of bit) onto the work piece. Handy for fluting wide columns.