This is a simple door lock. It can be used on vertical knobs. Suitable for child locks in rental properties, etc. Purchased in March 2025, one piece. This is one of a set of two, taken out of the bag but not used. Door Stopper Door Lock Set of 2 Stoppers Child Lock Safety Lock Door Lever Lock Fixation Door/Drawer/Door/Cabinet Opening and Closing Prohibited Door/Drawer/Door/Cabinet Opening and Closing Prohibited Baby Child Finger Pinching Mischief Prevention Earthquake Countermeasures (Black)