Print out the three parts. The mount fastens to the gauge with an M4x10 screw. The slider/pointer gets slotted in sideways then slid to the bottom of the gauge plate where there is a cutout to rotate the slider to the correct orientation (see back pic.) If the slider hangs, trim & sand the slider slot so that it moves freely.
Print the included 100mm gauge and pointer (Print @ 100%, no print scaling, only 1:1!) and attach with a little clear tape. Try not to wrap the tape around the parts because it may cause binding.
Snap the mount in place, snap the filament into the slide and push it so that the pointer rests on 0mm. Call for 75mm to be extruded and then read the gauge after the command is completed.
Adjust for the over/under extrusion based on the calibration instructions of your printer/controller.
Because filament, current printer calibration, mount length requirements vary... I have included the autocad files so adjustments can be made.
Don't forget to post the remixes.