I brought a nice carbon steel sushi knife back from Japan. I wanted to frame it and hang it on the wall, but also didn't want to damage so that it could be used. I purchased a shadow box and glued a thin plate of ferrous metal to the back of the box (facing the wall). I then attached a couple of magnets to the knife blade and centered it in the frame. The magnetic field penetrated the backing of the shadow box and attached the knife to the plate of metal I had glued to the back.
Most of the reviewers describe these magnets as being "strong" and "weak", but these are subjective terms. These magnets are made of Neodymium, which has a substantially stronger magnetic field than magnets made of other materials. Specifically, these magnets are rated as N45 magnets. Essentially, the higher the number, the stronger the magnet. For example, an N52 magnet has a stronger magnetic field; an N42 magnet has a weaker field. The vendor describes their magnets as being "less brittle" than competitors' N52 magnets, which is true. However, the vendor neglects to mention that their magnets are also weaker than the competitors' N52 magnets.
Regardless, the magnets are as advertised and do what they are supposed to do. They were packaged well.