Strictly speaking, it’s not a “thumb nail writer” unless it’s designed to be on your thumbnail. The term most associated with this kind of gimmick is the Swami. You can learn more about it in Corinda’s 13 Steps to Mentalism on page 4. But in short, it’s a device that is specifically made to allow you to write unseen by the audience. There are scores of wonderful examples from “C” types to modified thumb tips, boon writers to variations made from Sharpie pens or even banjo picks. One of the most well known booklets on the subject was written by Sam Dalal. If you’d like to learn more about this gimmick and how you can use it, get your free account now.