This was part of my DIY Whiteboard project, because my whiteboard is mounted near a corner which has a metal edge protector, I created these boxes with magnets to flexibly mount nearby. This is a very niche application, but perhaps it is useful to you, or gives you an idea for a solution in your own project.

There are two different models. These were designed around embedding 40mmx10mmx5mm neodymium bar magnets. The "short" model allows you to embed 2, one on each face of the corner. The "tall" model allows you to embed 4, 2 on each face of the corner.