Shame on you for suggesting such a thing - however I do believe rocks and bottles should be registered....../ sarc
No need to register them.
Just make it illegal for non-adults to possess them; and issue permits to carry to qualified adults, who have passed a saftey & proficiency course & background check.
Maybe a waiting period, and a limit on how many can be possessed; size/weight limits; how many can be obtained per month.
Make it illegal to artificially point, sharpen, or otherwise alter them....