Needed a SD card holder for my 3D printer and didn't see any that would work for me. I wanted at least a 4 SD card holder and wanted it to be easily removable if I moved my printer. There were a few designs that clipped over the edge of the door opening but would interfere with the door. SO I decided to start from scratch. The holder uses a rare earth magnet and simply sticks to the metal housing of the printer where ever I want to place it, this won't work on your printer if has a plastic, wood, or aluminum frame or housing to it.
I used some of the extra magnets I had from my GoPro Mag Mount
https://www.thingiverse.com/thing:1949608 that I designed. The link below is the site I got the magnets from but any 15mm x 5mm magnet will work. I used them because I had extras and also being rare earth type they hold very well. I used a dab of silicon in the hole to hold the magnet in place. The slots are also keyed (the 45* angle on the card is on the left) so they are always contact down and label towards you. Hit the LIKE button if you liked the design and feel free to comment also.
Magnets I used: https://www.apexmagnets.com/15mm-diameter-x-5mm-thick-disc
Nothing major, knock out the supports in the magnet hole.
Designed in 123D Design and Sliced and converted with Simplify 3D