On most interior door handles you will find a tubular mortice latch. An internal door latch allows you to close a door and keep it in place without locking it. For easy and smooth operation a strike plate will cushion the door handle and literally latch it into place.
Although they can come in different sizes the two most common sizes in the UK for internal door latches are 63mm and 76mm. These sizes are the overall length of the latch, or the case. When measured to the spindle mechanism, the backset, then they translate as 44mm for the 65mm case and 57mm for the 76mm case.
Whether you have lever on rose door handles or lever on backplate, your interior door handles can house any latch
How To Measure Your Latch
When buying a tubular mortice latch for your door handle it is important you know the correct size. Door handle latch sizes are usually advertised with their overall length, i.e the case. To measure the overall length of the latch case see diagram below.
Secondly, see below also to find out how to measure the latch backset size- This is basically where the spindle of the door handle will sit. Make sure you measure it to the central part of the backset.