When I am designing a new printing object I often have to add holes to the design thru which bolts can pass. Sometimes I want a clearance fit, other times I might need an interference fit. Measuring these bolts with a micrometer won't provide me with a value which takes account of the expansion/contraction that takes place when plastic is extruded and cools.
I therefore created a set of jigs which provide holes and gaps in the range 2mm thru 9.9mm, in 0.1mm increments. Together with a tray to hold these jigs I now have an instant means of finding the right size hole to suit the design, without actually having to measure anything.
If you have a dual extruder then you set set a height of 4mm in your slicer at which to change colour, so that you get jigs printed with coloured legends as shown in the photo.
Designed using TinkerCad.