When a hard-drive dies in one of my computers, I take it out and and pull it apart to get the magnets out.
Hard-drives have extremely strong and slim magnets. They end up in many useful places. One keeps my drill chuck in one spot… a half dozen hold notes and pictures.
I also have a couple on my shop apron. The magnet is on the inside and a metal washer is on the outside holding it in place.
It keeps my scribe knife nearby without putting a hole in the pocket. Sometimes they hold extra screws or some other ferous item. Its even strong enough to hold a wrench.