At age 6 or 7, I'd occasionally go around the house and gather various things -- shampoo, washing up liquid, cooking oil, food colouring, that kind of thing -- and then bottle some up in a bizarre-coloured mixture, with a label to the effect of "Burglars: drink this!".
We never had any trouble with burglars, so it must have worked.
A childhood belief about criminals

others believed things like this
- I believed that burglars ate soap & lipstick— Karen
- I used to believe that when I said my prayers, "God Bless..." meant please keep burglars awayAnon
- I used to beleieve (when VERY young; 12 actually!) that cat burglars stole cats!— Woody
- I used to believe that switching the light on and off was morse code to burglarsAnon
- To clean the goldfish you put washing up liquid into its bowl.— Sev
- Even though the title is 'How Bizarre', I always thought he sang "help is on"...Anon