Calipers are a useful tool because they provide a bit more accuracy than a standard ruler. This design is 3D printable, and can be modified to change the length, and increment size. It is nowhere as accurate as a digital caliper. But it helps to get rough measurements
when the ruler is printed on its back it becomes slightly warped, however this does not effect the functionality of the caliper. Printing the ruler on its side solves this problem.
make sure to calibrate your caliper with a standard before use