The "ring and dot" an ancient decoration... Take a cheap and nasty screwdriver and cut a slot in the middle of the blade. File each "tooth" to a point, one longer than the other. Push the longer point into the work as the centre point and turn the screwdriver so that the other point scribes the ring. Take cinnamon powder (or charcoal dust or whatever dark powder you prefer) and rub it into the marks. Sometimes oil rubbed on, sometimes a thin glue (depending on the surface) rubbed on and quickly rubbed off, fixes the powder in the design. Job done! It took longer to write this than making a ring and dot embelishment does!