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I just installed a standard deadlatch, very much like this:

enter image description here

The problem is, it can be opened from the outside with a credit card.

Of course, a properly installed deadlatch should make this impossible. When the deadlatch is depressed, the latch should not be able to retract.

But when I hold the deadlatch down with my thumb and wiggle the latch, the latch eventually retracts.

It has nothing to do with how the strike plate is installed or positioned on the door. I can do it without ever involving the door or strike plate. I can just use my hands. It's very repeatable. Just hold the deadlatch down, press and wiggle the latch, and it retracts, every time.

Does this mean I have a faulty deadlatch? How could a deadlatch malfunction in this way?

UPDATE: I have to use a latching lock for this door. That's part of the users' requirements. So a deadbolt is not an option. Covering the gap between the door and frame might be a good idea for preventing the credit card move. However, what I'd really like to know is how a deadlatch could malfunction in this way to begin with.

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  • Most that I've seen (whether or not they "should" act this way) will retract the main latch if the deadlatch is all the way "in" or all the way out, but won't if it's partly out, as when the door is actually closed. In any case, you either need a different lock or an anti-jimmy plate if it's actually "credit-carding" open, though I'm not clear that you've actually tested it that way, rather than with the door open and your thumb on the deadlatch. I'd personally go with a deadbolt, - harder to lock yourself out of and much more secure against carding.
    – Ecnerwal
    Commented May 4, 2017 at 18:50
  • Yep, I've tested it with a credit card. Actually works better than using your fingers, and the deadlatch in that case is, like you say, partially out but still in what ought to be a locked position. Covering the gap between door and frame could be the answer, although I'd like to avoid it if possible. A deadbolt isn't an option for this use case, unfortunately. I'd like to find out more about how deadlatches actually mechanically work internally, any recommendations?
    – Tom
    Commented May 4, 2017 at 19:23
  • The Schlage company is going to be less than pleased to find a picture of one of their locks illustrating a question about a broken poorly-made low-quality lock.
    – A. I. Breveleri
    Commented May 4, 2017 at 20:50
  • Yeah fair! Just replaced it with something more generic.
    – Tom
    Commented May 5, 2017 at 15:26

3 Answers 3

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If the strike bolt can be depressed by direct pressure when the small strike is not fully extended, then the lock is poorly made or broken. Replace it.

You should consider using a lock of higher quality. If this lock has failed, then perhaps all other instances of the same make and model are on the verge of failing. In any case, test the lock before installation.

If you really want to know the mechanical failure mode, you'll have to take the broken lock apart, and guess how it should have worked.

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If you look close you'll notice two "strikes"...a big one and a small one, side-by-side. The small one keeps the big one from moving, when it's depressed.

Maybe the small one is NOT being depressed when the door is in the closed position. Use a strike plate that makes the small one depress when the door is in the closed position. Check the alignment with the strike plate and make sure you don't have too big of gap between the door and frame. If you can still open it with a credit card, then it's broke.

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  • Unfortunately, this isn't the case. When the door is closed the "small strike" (the spring loaded half-cylinder behind the main latch which I was calling the "deadlatch") is fully depressed. I can see it clearly.
    – Tom
    Commented May 4, 2017 at 19:45
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What you should be looking for is a "Dead Bolt" lock. A dead bolt lock requires a key turn to secure the door from the outside. It can be secured from the inside either by rotating a knob or require a key. In either case the door will not lock without some intentional human intervention. They are not easily forced to the open position by credit cards, screwdrivers, slimjims, etc if they are properly secured. For safety reasons some local ordinances prohibit the use of double keyed (a key must be used to unlock even from the inside) dead bolts in homes.

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3
  • A deadbolt isn't an option for this use case. The door has to latch behind the person entering. Otherwise, yes, a deadbolt would be appropriate.
    – Tom
    Commented May 4, 2017 at 20:15
  • Is there a reason the person can't just turn the knob and lock the door after entering?
    – mikes
    Commented May 4, 2017 at 20:17
  • That's just what the client wants, I'm afraid, a door that latches automatically behind them.
    – Tom
    Commented May 4, 2017 at 20:18

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