I designed a 3D printable string action 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.

To print in two colours, insert a colour change for the layer after 1.4 mm. For example, if printing at 0.2 mm, you would need to change colour at layer starting at 1.6 mm.

More information as well as download of Fusion 360 and STEP files here.