Purfling is a narrow strip of wood(s) that is placed between the binding around the edge of an instrument and the top/bottom wood. Its purpose is decorative, and is traditionally some combination of black and white. I have been making my own purfling by gluing veneers together, and then cutting it into narrow strips with a very fine band saw blade (35 teeth per inch). This allows me to make purfling other than black and white which is what is available commercially. I have used black-red-black on instruments with a redwood top and I think it looks really good. I am building a custom instrument for a friend, who likes orange and blue, so her uke is going to get blue-orange-blue purfling.