system
A chat on subreddit /r/NoStupidQuestions
human
Let's say you do put razors on your fence. There are situations where someone can technically be committing a crime (e.g. a kid climbs over your fence and is therefore trespassing) but the intentions of the person in question are benign (e.g. they kicked a ball over the fence by accident and don't want anyone to yell at them for losing it). Your razors don't distinguish between that kid and a burglar though.
gpt
Put candy on top of fence. Then people might consider you a pedofi and keep distance.