i never know where are my rulers, and some of them are so damage that was impossible to find the 100mm LOL.

I decide to make this template that will allow you to mark the filament with a sharpie, or you can use electric tape.

How to use:

Place the tool over your extruder and place the filament inside the gap, then mark the filament the way you prefer, with a sharpie from the back of the tool or electric tape from the front.

Simple, and you will never need a ruler again for subject ;)

Happy Printing.