Just a simple gauge to help set the tension to the same level every time.  It was always a guessing game when setting the tension on my extruder. I would get it set where I like it. Then for some reason have to take apart the extruder. Getting the tension back to the exact level was not easy. So I created this little gauge so when I loosen the hinge I can set it back exactly where it was.  Once installed and you get the tension where you like it. Just make a mark so you will have a visual cue.