Where I worked they gave the mechanics pocket knives pretty regular. A friend of mine asked me if my five year old son could have one? I said yes because I think that boy was born grown. I told my boy that it wasn't a toy, it was a tool and should be used that way. I also told him that if he cut himself I would take it away until he was old enough to use it. About a week later I saw a nice straight light cut on his thumb and asked him what he had done to his thumb?
He looked me right in the eye and said "I hit it with a hammer."
I had successfully taught my son to lie.
I just couldn't take it away from him.