The tool is printed in two parts:

Ruler

The ruler is printed flat on the bed. This allows for a planned filament change to print the numbers in a different color.

Guide

The guide is available for different clearances. You can print the one that matches your printer's accuracy and glue it to the ruler. If you're not familiar with the accuracy of your printer, I recommend starting with the 0.15 versions and go from there.

Before gluing it in place, notice this part isn't fully symmetric. The side facing the ruler follows its profile while the other side has a chamfer going all the way around.