What are key-in-knob and key-in-lever door locks?
A key-in-knob lock is a lock housed within a door knob that is unlocked with a key. The lock and barrel mechanism are mounted inside the door knob with the keyhole facing to the exterior. The other side of the door knob typically contains a locking and unlocking button or dial, so that keys are not required every time you wish to open the door.
The key-in-lever lock operates in exactly the same way, but is housed in a different type of handle mechanism.
How do key-in-knob or lever locks work?
When the door is locked, the latch bolt is held strongly in place so that the door cannot be opened (i.e. the knob can't be turned). To unlock it, a key is inserted in the lock and turned. Without going too deeply into the internal mechanics, the ridges on the key align with wafers inside the lock tumbler until the wafers are clicked into place by the guide pins, allowing the lock to be opened. The door knob may then be used normally.
Where are key-in-knob or lever locks used?
These locks are usually found on exterior doors, as there is often little need to lock interior doors so seriously, although they can be located anywhere there’s a door knob or lever.
Are there any variations?
Though the styles of door knob or lever may vary, the locks within them are all fairly standard and will usually only differ by brand and the size of the lock required. As these locks are housed within the door handle itself, they are usually factored into the design by the manufacturer of the handle in partnership with a lock company.