To gauge the accuracy of my cylinder turnings, I built a homemade jig that’s easier to use than calipers. My jig is a 1/4″ thick plywood panel with lines spaced 1″ apart and parallel to the lathe bed. While turning, I simply sight over the top edge of my workpiece to compare its shape with the lines, which reveals any high or low spots immediately. My jig hooks in place on the lathe bed, but there’s enough clearance for the tool-rest to move freely. The jig also provides an ideal place to hang a story stick or turning diagram.