This is a PCB holders

You can add a circle neodyme magnet at bottom (15x2mm)
https://fr.aliexpress.com/item/20-pcs-N-odyme-Disque-Aimants-15x2mm-N35-Super-Fort-Puissant-Rare-Terre-15mm-x-2mm/32961401185.html?spm=a2g0s.9042311.0.0.46e96c37wgcyVM

I use springs with this specifications :
internal diameter : 6mm
external diameter : 8mm
Length : 28mm

Edit 2019-03-08 : I have updated the cale.stl file for better fixation
Edit 2019-03-08 : Add the the cale_grip.stl file for better handling
Edit 2019-03-19 : Add magnet (update photo)
Edit 2019-03-21 : Update base.stl and capot.stl (V2) for a better ergonomics
Edit 2019-03-21 : Add capot.stl (V3)