Here's how to make a diversion safe to store/hide small valuables or cash.
This version has a screw-off bottom, so that the whole thing can be picked up without falling apart and plaster makes it of comparable weight to its original contents to fool those that pick it up.
Step 1: What You'll Need
Epoxy (preferably quick-setting)
Plaster of Paris
Soup can or other type of can
Small(er) plastic jar with threaded lid (with label removed for mildew resistance)
Side-cutting Can Opener (did I mention it HAS to be a side-cutting type?)
Several hundred dollars in cash
Hungarian Vizsla (optional)
Step 2: Open Bottom of Can
With your fancy side-cutting can opener, open the bottom of the soup can leaving the top intact and remove the newly created lid.
Step 3: Clean the Can
Eat the soup, then clean out the can with hot water, but be careful not to get the label wet. Rinse off the lid and dry everything out with a paper towel.
Step 4: Pet the Hungarian Vizsla
Scratching behind the ears is best.
Step 5: Attaching the Internal Lid to the External Lid
Mix up some epoxy and put a glob on the inside of the metal lid.
Stand the small container upside down on the metal lid and center the two lids as best as possible. You can slowly spin the metal lid around to see that the small lid is aligned along the same center point as the metal lid.
Let the epoxy dry until it can be handled.
Now the plastic jar should fit in the soup can.
Step 6: Adding the Plaster
Mix up some Plaster of Paris. You'll only need enough to cover about an inch of the jar inside the soup can and if it's a little watery, it's easier to work with.
Pour the plaster of paris into the upside-down soup can then push the jar into the can and apply pressure so that the plaster makes good solid contact.
Wait until the plaster starts to set (2-4 mins) and unscrew the lid about a half to a full turn, then push down some more. This way when you screw down the metal lid in the future, it goes very snuggly in.
Let it sit for 20-30 minutes to solidify.
Step 7: Look at the Hungarian Vizsla
Look at the Hungarian Vizsla to make sure he's still interested.
Step 8: Use It
Put several hundred dollars inside and close the lid.
Let the Hungarian Vizsla inspect your work.