Installing the abalone and purfling rosette around the soundhole is one of my favorite steps in the guitar making process. It's nerve-racking and intricate, but I get to see a pretty dramatic change in a fairly short amount of time. It's starts with measuring and marking the soundhole, then determining the spacing for the various materials being used for the rosette. In this case I used two different widths of green shell abalone and one layer of black and white purfling. Each of these layers will  be spaced 3/16 of an inch apart. The circular channels are then cut with a router attached to a jig that rests on a metal pin coming up through the exact middle of the soundhole. This enables the router to act like a compass as it makes several perfectly circular cuts.