Not the most exciting design, but I love magnets and use them to fasten things all the time. I simply needed a hook on my fridge to hang a bag from. Not too much to ask.

This print uses a pair of 20mm x 5mm countersunk neodymium magnets that you can buy from any number of the usual purveyors of online neodymium magnets. You can either glue the magnets in place or do as I did, and simply melt them into place with the centre bit. Ideally use something made of brass to melt the centre bit as other metals can be somewhat “magnetic”.