Lasercut Rocketry Ruler

This is a ruler for drawing straight lines on tubes that are parallel to the centre of the tube, useful for marking fin locations on model rocket bodies. As a reminder that in model (and larger!) rockets the centre of pressure should be behind the centre of gravity these symbols are included! :) Designed to be lasercut out of 4mm ply in 2 sections. EDIT: Had a request for a 3mm version so have added one!