Apologies for the bad picture quality.
If you lose your calibration pin, you can no longer run your tool offset calibration… so make sure you don't lose it! This is a mount you can put on the 3030 aluminum extrusion to ensure you always know where it is. Made in onshape, my make was in Prusament orange PETG.
I used 2 M5x12 button head screws and 2 3030 aluminum extrusion nuts. The ones I used don't require you to undo any part of the assembly: https://www.amazon.com/gp/product/B09B3HWXPW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
The author marked this model as their own original creation.