You can hide for example your car keys under your car when you go hiking or running and you don't feel to bring them with you, or a spar pair of your house keys anywhere in a metal box or under any metal surface.
YOU MAY WANT TO PAINT IT BLACK OR GRAY TO CAMOUFLAGE IT BETTER.
Step 1: WHAT YOU NEED
-stripes of strong magnet;
Step 2: MAGNET
glue them to the back of it.