Those designs are a series of adaptor to securely fix various tools on magnetic bases.

Magnetic bases like those: https://www.amazon.com/Magnetic-Adjustable-Indicator-Holder-Digital/dp/B00L5T2ZA8 are very handy to hold various types of tools as they are very stiff, but easy to position on any paramagnetic surface. However they are designed to be used with dial indicators and do not easily adapt to other tools. So i designed adaptors/holder to use with some of my tools including a pocket microscope, a torchlight and crocodile clips.
The torchlight and camera holders in particular are print in place and should adapt to any cylindrical tool you may want to use (contact me if you need other diameters). 

The crocodile clip holders use a 5 mm diameter 4mm long M3 heat insert and an M3 screw. I added one of those handles on the screw for easy manipulation: https://makerworld.com/en/models/55516#profileId-57079 (chose the type depending on your preferences)

Edit 03/2025: I added another holder for 12mm “pen microscopes”. See the "tube microscope holder" files and the last picture for illustration. It uses a 5*5 M4 melt insert and a 10mm M4 screw.