A Classic retro bicycle wheel lock.

It attaches to the frame with two fasteners and screws (included).

While unlocked the key remains on the lock; when you lock the wheel then the key van be taken away with you.

This is a supplementary only lock. Mainly it is used when you want take off your bike for a very short time (just to take a coffee for example) and even then you should still keep an eye on your bike. After all consider that even heavy steal old timer bikes are not too heavy for someone to take them by just lifting them.
So as a supplementary lock is ok and it is very beautiful piece of bike accessories too.

It measures as per diagram attached.

Any further questions are welcome.