Easily measure and set sag on your mountain bike fork. This is based on a previously commercially available product called the saggle, which appears to no longer be available. You can use a regular ruler of course, but this is more fun!
Works with travel (mm): 100, 120, 130, 140, 150, 160
Just use the appropriate side of the tool to measure your O-ring position. The number should be on the end nearer to the headtube.
Large marks at at 10%, 20% and 30%.
The author hasn't provided the model origin yet.