If it’s a Yale latch lock and it’s on the right-hand side of the door, then a loose snib might just have fallen down when the door was slammed shut. (The snib is the tiny button or lever that holds the bolt open or closed. A dropping snib on an ERA on the other-hand, is only going to lock you out if it’s on the left-hand side of the door. (These handings are as if you’re standing outside.)

Another possiblity for any lock with a snib is that there’s a huge gap between the door and the frame; and you left the lock snibbed yet managed to slam it shut.

One, more disturbing possibility you should bear in mind however, is that if a thief has broken in through a window or throught the back door, (s)he will usually snib the front door’s latch so as to get some warning if you return.

So, enter the premises cautiously. Send the dog in first.

If you’re choosing a latch lock, some can be snibbed open or closed, but some can only be snibbed open (also known as a hold-back).

I would avoid bi-fold, i.e. concertina doors. They seem attractice for nice days. Lots of light coming into the kitchen-dining room. A garden and a kitchen that are almost one.

However, unless they are of the highest quality and very expensive, they tend to go wrong. Either they are on tracks, which will tend to sieze up; or they all hang off one poor set of hinges which are never strong enough. All doors move with the seasons and the chances that the bolt holes and keeps will line up with their bolts for a long lifetime are poor. Many lunatic manufacturers put a lock near a closing hinge such that if you forget and leave the key in and then open to door, the key gets broken and the door gets chunks gouged out.

They’re also murder to work on. There’s very little that I could repair. Mostly you have to get the fitters or manufacturers back; and of course, they’ve gone out of business.

And they are difficult as far as insurance is concerned. When most policies are describing what is acceptable in the way of security, it’s usually unclear which category bi-folds or concertinas fit into. So there’s plenty of wriggle room for the insurers to get out of paying your claim. And most of the candidate categories that they might fall into would tend to specify key operated bolts anyway; whereas only about 1 in 5 have key operated bolts.

Have a look at any draught-proof strip that might be there. Maybe it’s too thick and should be replaced with thinner. Most draught strip is stuck or pinned in place. Be careful though: it’s occasionally part of the door stop (the part of the frame that the closing door stops against).

If it isn’t the draught-proof strip then maybe you should get a locksmith to come and sort it out.

(Don’t leave ladders around of course. Lock them somewhere.)

So I got in and the lock did turn out to be the one I suspected. I picked the inside tumblers which is easier on that model than the outside tumblers and got the door open.

It turned out that a new flat-mate had deadlocked the top lock when they went out. There’s a risk with any lock where a key can deadlock it from the outside cylinder and where a separate key (or no key at all) is built into the lock. Normally when the outside cylinder is changed, people don’t want to pay to have the inside tumblers redone such that the one key continues to operated both sides. Then of course, the inside key hardly gets used and is eventually mislaid. And then a new flat-mate exits and deadlocks someone inside.

So when new people move in, don’t assume that the locks are obvious. Ask yourself whether they could lock you in (or out) if they were to do something that you normally didn’t do. Another example last week was where some new people moved into the other apartment sharing a mini-vestibule with a lockable door. My customers had never had a key to the vestibule door, but the estate agent had found a key for it and given it to the new occupants of the other apartment. And of course they locked my customers out and went away for the weekend.

When considering the locks on your doors, you need to strike a balance between security and safety. You want to keep thieves and other scum out, but you don’t want to keep yourself in should a fire break out. (There must be other internal hazards you might be in a hurry to escape from, but fire is the main one.)

If you deadlock your front door whilst you’re in, you run the risk of not having your key on you when you reach the front door with flames behind you. (Deadlocking means “you locked it, you unlock it”; it’s the opposite of a sprung or “live” lock.)

It’s obviously not a good idea to keep the key in the lock, even if there’s no letter-slot. “Yes but I always leave the key on the hall table.” Again that’s a security risk if you have a letter-slot; and Sod’s Law says that it won’t be there the day of an emergency — someone couldn’t be bothered to find their key when they left that morning so they took the spare.

If you must deadlock your front door when you’re inside, get a break-glass box with a spare key inside, near the front door (but not reachable via the letter-slot).

The best option is the simplest: traditional bolts. Don’t get titchy little ones, with titchy little screws. Get some thumping big ones with decent sized screws, especially the screws in the staple (the part that holds the bolt when it’s been thrown).

Imagine you’ve broken into a house and you’re one of the top 10% of thieves, intelligence-wise, i.e. you’re IQ has just struggled over 50. You find a set of keys. It doesn’t matter if, sensibly, there’s no label. You’re going to try …

So, don’t leave keys with next door neighbours. Leave them with someone close but not that close.

(Anyone remember a film portraying Buster Edwards as a, mostly, lovable thief? I hated that film. Thieves blight lives. End of story.)

You may have a Mul-T-Lock door. If you look around the handle fittings you’ll usually find the name there.

The good news is that if you do have such a door, you have a very good door and lock system—pretty strong and secure. Your letterbox, for example, is probably a long way from the lock and is protected by a nice strong cowl.

Around here, most of these doors are on properties that were once owned by the local authority.

The “bad” news is that changing the cylinder is a little more expensive. This winding business is done via the cylinder (a euro- or “pear”- shaped cylinder) having a cog-wheel to do the work. (A regular euro cylinder has a cam that “flips” the lock rather than winds it.) These unusual cog cylinders are nearly three times the cost of a regular cylinder.

The other thing, and the main reason for the post, is to note that, apart from the cylinder, the door and lock are an integral system. If you’re buying a place with a Mul-T-Lock door, try to obtain from the sellers, especially if it is the local authority, details of who can repair/replace the door. I can’t you see.

You get into your car in a car park and start it up. You reverse out of your space and see a note stuck to the rear window. You get out to retrieve the notice, the scumbags then jump into your car—engine running and unlocked—and off they go.

So if you’ve just got into your car and are moving off, don’t be persuaded to stop and investigate any little peculiarities. Wait until you’re a good distance away before you investigate. If you must stop just after you’ve moved off, be very careful. Have a good look around from the inside with the doors locked first. If you must get out, try to wait until a family is in the vicinity and then switch off the engine, take your keys and take your purse.

I had already heard of another much scarier scam. You start to reverse, there’s a scream, you stop and leap out only to find someone under the rear of your car. But you didn’t hit them. They were hiding; they screamed first and then slid into place after you stopped.

If you’re a tradesperson in the UK you may well have received a nuisance call from the same bunch. I’m sure they pester plumbers, decorators, etc. just as badly. They open with “I’m calling from BT and I’m looking for a locksmith/plumber/whatever.” Of course they’re not. They’re looking to sell you website building or “optimization”. And if you take only a short look at the results of a google search on BT Customerstreet, you’ll struggle to find any happy customers; the only positive stuff you will find is BT Customerstreet’s own copious blogs which seem to be trying to crowd the complaint blogs and sites off the front few pages of google searches.

The other very annoying thing is their ignoring of the Telephone Preference Service or TPS. If you haven’t signed up with TPS, you might consider it. It does actually reduce the number of nuisance calls and cold calls that you get. A surprising number–the majority in fact–of telephone marketing and sales companies respect the TPS. But not BT Customerstreet.

Being BT they claim, with near certainty of being half right, that you are already a customer and therefore not covered by the TPS.

Anyway the good news is that the Office of Fair Trading have received several complaints. MPs have received complaints. Trades organisations have received complaints. So maybe something will happen to curb this unpleasant bunch.