Why are locks handed?

The term 'handing' related to the direction in which the door travels when it is in use. We need to know about handing in order to ensure the products they supply will be suitable for the doors to which those products will be fitted.


Some items of door hardware will only work on doors of a particular 'hand'. Therefore, it is important to ensure the correct handing is supplied.


In particular, we are going to be exploring lock handing. When it comes to handing, some locks are handed. We may ask “Please confirm whether you need this lock to be right or left-handed.”

Sometimes it seems ironmongery is made unnecessarily difficult – but we promise this isn’t done on purpose! 


Some locks are handed because it’s critical to their function, and it is important to ensure the door closes and locks correctly. 


For example, the below lock is a mortice night latch, typically used for apartment doors. The handles are connected by a split spindle, where the inside handle has a key function of retracting both the latch and bolt – allowing immediate escape.

The outside handle will not grant such easy access – you’ll have to use a key to unlock the door first. You’d need to determine the handing before buying to ensure the internal handle is free to escape.



Essentially, locks are handed to enable a bevelled latch to face the striking plate.

This way the latch goes over the strike correctly and allows the door to open and close.


Locks can sometimes come with reversable latches which can be adjusted on site – check that the lock is dual handed.

Never open a lock case yourself as it will ruin its warranty!

How do e determine handing? Please use the below diagram to assist you.

ISO = method adopted by the GAI (Guild of Architectural Ironmongers)

DIN = method used in Germany and for windows and pedestrian doors under BS EN 12519.

ANSI = American method