You say: "What is this cache, if you have already written about this?". Perhaps so, but I think that in most cases (interest 98%), this method will save your jewelry and money in integrity and safety.
It looks like this: the metal guillment inside the door - in the upper end
To make such a cache, you need a metallic (aluminum or plastic guillo, from which PET bottle is made), a metal screw with a gash, drill with the drills of different diameters.
In the lid we drill a hole and screw the screw "Stand", metallic to it - to get a cache with a magnet.
In the door, drill a hole with a drill, and then the sleeve to the insert into it. Process the edges so that everything is exactly)
We try on and get our cache. Everything is ready - you can use.
Such a small men's thumb)
A source