Security thumbturn for euro cylinder lock

Question

My front door has a mailbox slot which makes it really easy to operate the inside door handle from outside with a long object. One solution I'm considering would be a mailbox secured to the door over the mailbox slot. Another option I'm considering (possibly both) is always locking the door from the inside. However, for fire safety reasons I would need a thumbturn, which would lead to the same issues. Hence I was wondering if there is such a thing as a security thumbturn that's a bit harder to open with burglar's tools?

Of course everything can be opened with sufficiently advanced tools, but I was hoping there were thumbturns that were designed to at least be slightly trickier to open than the default design, e.g. by requiring some finger dexterity that burglar's tools are unlikely to have. Is there such a thing and does it have a generic name? "Security thumbturn" isn't giving me a lot of results.

Answer 1

Rhetorical questions that bring amazement:

1. Can an adult actually get his arm through the mail slot up to the elbow to reach the doorknob without getting his arm stuck? If so, that's a massive fail in the mail slot design and someone should have his knuckles smacked with a ruler for that!

2. Did someone actually install (or was it purchased that way) the mail slot that close to the doorknob? If so, that's a massive fail in the mail slot installation and someone should have his knuckles smacked with a ruler for that!

Suggested Answer:

1. Have you considered a simple guard installed above the slot to, effectively, make the door "thicker" in that spot, requiring more arm through the slot before the elbow can bend upward to reach for the handle? It might look something like this lovely bit of ASCII art. (Looking at the narrow edge of the door)

Inside         Outside

      |   |    This is the door
   ---|---|    This is the top of the slot with a guard above it
      |   |    This is the slot
      |---|    This is the bottom of the slot
      |   |    The rest of the door

Make the guard bit (--- in the drawing), extend toward the inside as much as necessary. A would-be thief would have to get his arm far enough through the slot to get his elbow past the inside edge of the guard before bending it up to reach for the doorknob. This means that the bicep/upper arm has to fit through the mail slot. Most adults, with arms long enough to reach from the mail slot to the knob, would have arms too big to fit that far through the slot.

Of course, you could hang a basket for the mail from the guard so that the mail moves with the door, or even a full-on mail box there, too. Do remember, the basket/box needs to be tall enough that someone can't reach through the slot to steal the mail - that'd be almost as bad! (And is probably why mail is simply allowed to fall to the floor).

---

Alternate suggested answer:

In response to the desire to make it difficult to turn the deadbolt (thumb turn) with a coat hanger or other object stuck through the mail slot, I'd suggest a "child safety door knob cover" that would be placed over the thumb turn. Something along the lines of this item (image sourced from Amazon)

While ugly, any such cover, would, if sized correctly make it nearly impossible to operate the latch with a simple tool being wielded blindly through the mail slot, yet allow for easy operation of the deadbolt by nearly anyone (except, of course, for a small child, against whom it's designed to protect in the first place) if/when it comes time for an emergency egress.

These are usually soft rubber that are easily squeezed to enable anyone from the age of 6 (or so) on up to grab, squeeze, and turn the knob underneath, while preventing simple operation by something unable to provide the necessary leverage to do the squeezing.

Answer 2

You, without realizing it, kind of answered your own question about the "security thumbturn" not giving a lot of results, FIRE SAFETY. Any type of thumb turn that would be "tricky" to turn could be a real problem for children and elderly persons to operate in an emergency. We have fire inspectors routinely give home safety lectures and this is one subject that always comes up.

Your best bet would be to secure your mail box or disable it and install a mail box somewhere else. I'm actually surprised the Post Office hasn't approached you about this because they don't like to get out of their trucks now.

Answer 3

The usual recommendation (speaking as a locksmith) is that, if you are really concerned about this, you should consider a double-cylinder lock with a "thumbturn key" kept in the inside lock whenever anyone is in the house, or at the very least hung on the wall adjacent to the door, at a height kids can reach, perhaps with a chain just long enough to reach the lock so you can guarantee it won't walk off but it will still be available when needed.

In fact, some companies have make this into a product -- a thumbturn body that attaches to a key, with the key modified so it latches into the lock when inserted and requires an "ejection tool" to remove it. That makes it look more like an ordinary thumbturn, prevents it from walking off, but still permits removing it when necessary. I don't know if anything along these lines is currently available on the market; I haven't kept up with the trade in the past decade or two... but an active locksmith should be able to research it for you.

Answer 4

Stumbed here for the same reason, worse we have a cat flap. Dont want a key on the inside as its fire risk if we deadbolt at night and cant leave without a key, and if leaving key in lock might aswell have a thumbturn. Anyway, I have explored letter box shrouds, but there is no security available for catflaps. But discovered this: https://tradelocks.co.uk/kinetica-3-star-kitemarked-child-safe-thumb-turn-euro-cylinder-locks.html It is a thumbturn that requires a double motion to turn. Marketed as a childsafe feature, their documentation also states it prevents against common attacks, which i can see as the leverage to push the thubturn is going to be difficult with a coat hanger! Its also a decent lock outright. Heres it being picked: https://www.youtube.com/watch?v=C0CZhBjTlhU&ab_channel=LockNoob