This is a bridge in Paris. You hang locks on it with the name of you & your boyfriend/girlfriend/best-friend then throw the key into the river. So even though the friend/relationship may end, you can’t remove the lock. It stays there forever
The "Love Lock" bridge in Hamburg Germany is just cool. You buy a lock, have the local jewely etch your names on it, lock it onto the wire of the bridge and together toss the key in the water. I was a neat experience.