I bought these coin-sized magnets for some project and didn’t use them.
They were just stetting away from anything magnetic-sensitive, till one day I was trying to figure out where to hide a key and my brain did a 2+2 and came out with sticking one of the magnets to the key and just find a suitable place.
It worked better than I expected. And the funny part is that you are not subjected to place the key where there is metal, but you can add a metal “location” by simply adding a wood screw to any part of the house you can think of for hiding the key, just make sure it is flush with the surface, your fingers will thank you. Do you want to rotate locations? Fine. Select several places, install screws and you are done.
There is also the obvious way of just selecting a hidden spot and affix the magnet to it: it also works. I am using both ways just fine.
And unless you are way too obvious, it would be very hard for somebody to find the key easily or at all.
Along the same lines, I used a magnet to hang a yellow jacket trap from an aluminum gutter – turned out a 4″X4″ galvanized electrical box cover just barely fit snugly in the bottom of the gutter, providing a ferrous material to which a hefty magnet could be attracted.
I have used those rounds and they are very handy. I have also used https://www.amazon.com/gp/product/B0B3X78GFH/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1 for various purposes including holding small to medium sized tools, holding doors closed, and keeping a trailer chain from dragging but available at a slight tug. Note the 2-part aspect.
I discovered a while ago that tiny round magnets can easily be embedded in the plastic bows of keys that have those annoyingly bulky plastic bows, as so many do nowadays, making the keys convenient to stash wherever there’s a steel surface.
I hadn’t thought of using screw heads to create storage points – that’s a good one.
I can recommend K&J Magnetics ( https://www.kjmagnetics.com/ ) as a source for magnets in a wide variety of shapes, sizes and strength, as well as good tutorials and information. I’ve used their magnets at work and at home.