English to Persian (Farsi) Art/Literary Poetry & Literature

How would you translate "when she heard the bolt snapping back"?
In case you're not sure what a bolt looks like, you can a picture of it through the link below.

https://image.shutterstock.com/image-photo/silver-door-bolt-...

"Ro!" called a friendlier voice on the intercom. It was Myra. "wait there, we have the manual bolt on the door"
Ro waited at least a minute. When she heard the bolt snapping back and the door opening, she looked down where she expected to see Myra.