Mortice door latches and locks come in different sizes and working out the right one for your door can be tricky. The most common sizes in the UK for internal doors are 63mm and 76mm. This is the overall length measurement of the latch, often referred to as the case. This size will be determined by the size of your door and where you would like the latch to be inserted. You may have a panel/stile or detailing that will restrict the size you can go for.
The backset measurement is also an important thing to consider when choosing latches and door knobs/handles. The backset is the distance from the edge of the door to the spindle mechanism on the latch. Usually a 63mm case measurement will have a 44mm backset and a 76mm case measurement will have a 65mm backset.
The backset you choose is where your door knobs will sit on the door (where the spindle goes through). You may want your door knobs to sit centrally to the door stile, or if you have chosen door handles you may want to offset them slightly to take the lever into consideration. The backset measurement is also important so you can ensure that when you turn a door knob you do not hit your knuckles on the architrave. When deciding on replacement door knobs, check the backset measurement on your existing latch and the diameter of the door knob to ensure there is enough room for your hand to turn the door knob.
All our handles are supplied without latches or locks as there are so many variations and we find our customers often already have latches/locks on their door they'd like to reuse.
If you have mortice latches or locks in your doors and they seem in good working order then it is worth checking if they are heavily sprung. The majority of our door knobs and handles require a heavily sprung mortice latch or lock to work correctly and return the handle back to its original position once turned.
To check this, remove your current handle and operate the knob or the lever and if it returns on its own this means your current handle is sprung and your latch/lock is unlikely to be. You would need to choose a sprung handle/door knob in this case or change the internal mortise latch or lock to a heavily sprung mortice lock or latch to work with un-sprung handles and door knobs you may wish to buy. Be aware that many mortice latches are titled heavy duty latch or lock but this does not refer to it being sprung.
Download a PDF version of our measuring for a door latch guide here