The most important parts of a mechanical lock are the opening mechanisms (knob, trigger, key cylinder...) and the locking mechanisms (bolt or bolts).
The lock body incorporates most of the mechanisms. The key cylinder has a slot where the key is inserted, which can be security or serrated. The bolts allow locking when turning the key, providing security to the door.
It can incorporate a trigger for opening from the inside. The counterplate is the only piece that goes outside the body, it is responsible for housing the bolts when they are outside to block the passage.
