I designed a 3D printable gauge/ruler that can be used to measure the string action on a guitar or ukulele. It features measurements in both millimeters and fractions of an inch. It can be optionally printed in two colours (does not require a multi-colour capable printer). Or print in single colour and use a sharpie to fill the depressions.
![](https://arcady.genkin.ca/wordpress/wp-content/uploads/2021/08/cad_rendering.png)