Despite looking a bit rougher than most of its contemporary counterparts, it functions the exact same way as a modern version. Usually came with a handy hole so it could be worn on a keyring.
There were also much smaller keys which were worn like rings on a finger, but those were for smaller locks like ornate lockboxes and the like.
Well that's probably the coolest thing I've seen today. Is a matching lock still around?
I was curious as well and found this article online about ancient locks and keys https://imperiumromanum.pl/en/article/keys-and-locks-in-ancient-rome/amp/