A transparent film ruler for models that measures extremely narrow widths and circles
A tool that measures the width of a groove by printing the actual line width on transparent material.
If you want to re-engrave the groove made in the plastic model with
a tool, but you do not know which width tool fits, put it on the place you want to measure as shown in the figure
and check the size of the matching width.
You can upgrade from the actual inspection with a tool to the groove to more accurate measurements.