I needed a large-scale beam caliper to take some body measurements. I happened to have some 20 mm wooden dowels lying around, so I designed some jaws to allow for measuring.

To assemble, insert the two thumb pieces until seated into the pockets of the moving jaw. The static jaw should be press fit onto one end of the dowel, then the moving jaw can be slid onto the other end. To move the jaw, depress the thumb pieces toward each other (in a pinching motion), then move the jaw to the desired position.
 

After taking the measurement, a ruler, meter stick, or tape measure can be used to determine the distance between the two inner faces of the jaws.

If the thumb pieces break, there is a small hole that allows for any pieces stuck inside the pockets to be removed. A bobby pin (with the safety tip removed) can be pressed into the hole to eject the broken piece (will require the pin to pushed against a hard surface to push it inside).

Printing Notes:
These parts print without supports and should not require any post-print cleanup. I recommend printing the jaws themselves on a smooth build plate (to make the measuring surface more accurate) and thumb pieces on a textured build plate to give them some tactile feedback when using the moving jaw.

While I used PLA in the pictures above, it should be noted that PLA will deform over time and cause the moving jaw to become more loose over time. Ideally, a less pliable material should be used, but this is unnecessary for one-time or few-time applications.

Parts Required:
 - 20 mm Dowel (like https://www.amazon.de/Vasalat-Holzst%C3%A4be-glatt-Basteln-Inhalt/dp/B09P3NF277/)