In your younger days, you might've used a shoebox to store and/or hide your trading cards (whether of the baseball, Star Wars or Pokémon variety), Halloween candy, your weed or even your sneakers. As a grown up with passports, cash, weed and other adult valuables, you don't need to ditch that classic and familiar form factor.
Though it looks like an innocuous cardboard container, The Mandem Safe secretly hides a 5mm folded steel interior you can access via a key-driven cam lock. To help ensure no one swipes your crafty little locker, it comes with holes pre-drilled in the base so you can securely screw it right into the floor (or closet shelf, or whatever).
This clever cache appears to just be in the prototype stage right now. But you can express your interest in the producers making it a real product on their site.
In the meantime, you'll just have to rely on hiding your goods under the mattress, in your underwear drawer (because no one ever looks there) or inside that fake rock you have that looks remarkably like a fake rock.