Even one of the locksmith bulletin boards I’m on can’t get this one right!
A rim lock is one that is fixed to the inside face of the door. (Although it would not surprise me if one of the national call centres’ operatives, whose work I was tidying up after yesterday, had fitted a rimlock to the outside face of a door! Remember: the nationals are good at advertising and staffing call centres in a “cost effective way”; they are not good at locksmithing, plumbing, carpentry, …)
The alternative to a rim lock is a mortice lock. This is one that has been fitted into a chiseled-out hole (the mortice) in the door. As long as the door’s thickness is 44 mm or more, a mortice lock is usually more secure.
A different kind of classification (and this is where even my trade association’s bulletin board gets it wrong), is the way in which the lock works: most often the tumblers are either pins or they are levers. And normally pin tumblers are fiddly and small enough that they are encased in a, usually removable, cylinder. So pin tumbler locks can usually also be called cylinder locks.
The most common pin tumbler cylinder lock on wooden doors in the UK is the five-pin Yale. The most common mortice lock in London is the Chubb 114, which is a five-lever mortice lock.
Often, but definitely not always, a pin tumbler/cylinder lock is a rimlock and a lever lock is a mortice lock.
Well, if you care, hopefully that’s been of help.
Oh. Back, briefly, to the nationals. They are the ones with the huge adverts in the phone books where there are no local phone numbers visible. Naturally, I am going to say that 90% of the time, you’d be better off with a local tradesman (I wish I could say 99%, but there we are; I’d also like a Goldwing for Christmas). And if you are a local tradesman who’s kindly offered an 0800 or 0845 number, my advice would be to show your landline number as well, so that people can have confidence that you are local.