I'd get a bigger lock box. Preferably with a combination lock so you don't have to worry about a key or something. A simple 4 digit code is easy to remember, and cracking through all 10,000 combinations would take your eight year old long enough (unless he's a genius) to where you can catch him and scream at him, etc. It's what my mom uses to hide the $20,000 I'm not supposed to know about.

See if you can get one with a false bottom while you're at it. That way if he ever does crack it open and find only love letters he'd be disappointed.

Still, I think the damage has been done. At least he didn't find it in his dad's bedside drawer when he was 13 like a friend of mined did. Scarred him for life.

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Well sir that seems to be someone else's problem.