This is a 3D printable protractor assembly that can be easily added to our Compressed Air Rocket launcher: https://www.airrocketworks.com/wp/shop/ This angle gauge will accurately identify the angle at which the launch tube is set. Ideal for teaching ballistic trajectory and for use with physics competitions. We offer an educators discount on our launchers, just ask! Print one gauge (light color), one compound wedge (any color) and one pointer (dark color) for best contrast. Use ultra fine point sharpie to make gauge numbers and degree marks more visible. Refer to video for installation. Use large flat blade screw driver to drive wedge into place to clamp the protractor to the wooden stand. It should only fit one way due to the double angled faces. For a quick video on how to assemble the components to a launcher, take a look at this video: https://youtu.be/tuUAXpKJQfs