A regular job for a handyman is dealing with doors. Almost every door in the world has a latch to keep it closed or maybe a lock in addition to the latch.
Basically in the UK there are two sizes of the important dimension—this being the distance from the side-facing plate on the latch to the centre of the handle spindle (and/or keyhole). Since this is what you can see and easily measure before you take out the worn latch to be replaced, it would be very useful if this was the measurement always quoted …but far from it.
This measurement is known as the ‘backset’ and it used to be 1—3/4 inches or 2—1/4 inches in old money. These days it is usually either 44mm or 57mm (the metric equivalent).
However, look at a trade site or DIY outlet and they will say the overall measure (often 63mm or 76mm) which is effectively the depth of the hole required to accommodate the lock or latch. This is relatively unimportant since who cares how deep the latch goes into the door so long as the spindle hole or key hole line up with the handle?
And even the backset is commonly quoted as 46mm or 56mm instead of 44 and 57 like a millimetre or two wouldn’t make a difference.
So come on lockmakers, Willenhall (West Midlands) was the epicentre of lock making worldwide at one time surely we Brits can standardise to stop confusing everyone.