The Master Trainer is the essential tool for the Tracing exercises in Free-Motion Mastery in a Month. Buy the Longarm size if you will be quilting on a frame-mounted longarm quilting machine. It can also be used to train for a sit-down longarm machine where you move the fabric -- the larger size lets you use a wider hand position on the fabric around the needle area.
In addition to its function as a muscle memory training tool, the Master Trainer also can be used as a quilting ruler. The straight edge does straight lines, the rounded side does small curved grids and block outlines, the wavy side does S-curves and the bumpy bottom edge does clamshells. Instructions for each are part of the daily lessons in the book and the video class.