First you need a small and big spray can
open the top of the big one with tools
put tape around the opening that the plastic part clamps
last but not least put the small spray can in the plastic part of the big one and put it in each other.
A deo spray used as money hiding place or deo spray converted to money safe box
There was a book I remember from my youth that was entirely devoted to "hidey holes" like this - little places to hide things in plain site. Loved that book, got so many cool ideas from it. This reminds me of the kind of thing that was in the book. Wish I could remember the name of it - love to read it again. Dude even had suggestions on how to hide a house using mirrors on a long, wooded driveway.