Locksmithing and Security

The “French” doors you usually find in the UK are not French at all, as you’d probably expect. As you close proper French double doors they fit together by one door having a rounded edge profile and the other door having a cupped edge profile. When they’re properly sized and when the wood is properly seasoned, prepared and painted so that it doesn’t expand or shrink too much, this is an excellently draught-proof arrangement. Naturally it’s getting harder and harder to get proper doors that are properly fitted.

Here in the UK, “French” double door fit together with rebates. The edges where the doors meet have L-shaped profiles. This is nearly impossible to draught-proof.

Fitting locks (deadlocks or sashlocks) to either countries’ arrangments is challenging. Normally a rebated door will have a rebated lock. The lock will either be specially shaped or will have an adapter such that the bolts and keeps (boltholes) can still be placed centrally, across the rebate.

A lazy or ignorant fitter might be tempted to fit the lock off centre so that they don’t have to deal with the step shape of the rebate. Unfortunately this means that the bolt keeps will find themselves in the thin and fragile sticking out part of the other door. And the lock case will be too close to the face of its door and easily broken out and opened.

Even when fitted properly rebated doors won’t be secured particularly well by a deadlock or sash lock. Most deadlocks and sash locks, for example, lose their BS (British Standard) rating when used between rebated double doors.

You really need to fit mortised bolts as well. Mortised means that the bolts are inside the door rather than screwed to its face. They are also known as rack bolt or star-key bolts because a star shaped key that goes into a small hole is used to wind the bolt in or out.

What does it mean when a lock is BS (that’s “British Standard” rather than bullshit)? Does that mean that my insurance company will be happy? (This post is largely addressed to the UK.)

Well you can be fairly sure that a BS lock is reasonably good. However, the reverse does not necessarily apply. Just because a lock isn’t BS, it doesn’t mean that it’s of lesser quality. Two of the best locks ever — the Ingersoll SC71 and the Chubb 110 have not been BS for much of their career. Yet if you have that pair of locks on your door, a skilled locksmith will have a very tough time getting you in, so a thief is in for an almost impossible time. Although as we’ve said many times, the locks on the front door are only secondary in importance to physical strength of the door and frame, the illumination, the state of the window locks and what’s around the back.

It doesn’t necessarily mean that your insurance company will be happy either. I’m afraid you really do have to read the policy. The commonest thing your insurance will ask for is a five-lever mortice deadlock on the final exit door (the one you can’t bolt from the inside because you will be on the outside). It might go further and ask for a BS 3621 five-lever mortice deadlock. It might just ask for a BS 3621 lock.

If you do have the excellent Chubb 110 and your insurance policy asks for a five-lever deadlock you ought to get written confirmation (good luck) that the Chubb 110 is acceptable (as it should be) since for technical reasons lost to the mists of time, Chubb decided to term the 110 a five-detainer lock. It is, as I’ve already mentioned, at least as good as, if not better than your typical five-lever lock.

Not all mortice deadlocks are lever locks. In the States, for example, very few locks are lever locks. The other main kind of lock is a pin tumbler lock. Your Yale latch lock will almost certainly be a pin tumbler lock. So what? Well if you squint into your pin tumbler lock’s keyway, you will actually be able to see the pins. They’re little brass pins of a couple of millmetres diameter. If you can see them though, you can attack them. The lever tumblers of a lever lock are deep inside the lock and way more difficult to attack.

It could turn out then, that you have a pin tumbler cylinder operated mortice deadlock on your door. If you have, its key will not be the traditional “keyhole” kind of key with a blade and a stem. Instead your key will be a “Yale” style key turning in a cylinder and with the cylinder operating the deadbolt. Again, if your insurance policy asks for a five-lever mortice deadlock, then you might not be covered. Get written confirmation.

If you have a pair of keyed-alike (same key operates both) Banham locks, which are quite common in London, and your insurance asks for a five-lever deadlock, once again you should get written confirmation that your locks are acceptable. Banham do produce a fine lever lock but the typical pair of Banham locks encountered on London doors will both be cylinder operated and neither, therefore, will be a five-lever lock.