I wanted to make sure I really had the hang of cut loops because for some reason, they were giving me a lot of trouble at the start. So after completing the pyramid railing extra challenge, I decided to give this a shot.
It was good practice in inset faces, face extrusions, cutting out edges and replacing faces, and for the lock, a lot of messing around with a torus. I even got to use the snap tool to get the front of the torus to line up with the front edge of the lock.