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Can anyone help me with terminology to describe two different types of functioning in a door lock. (Please note, I am not talking about a lock that is broken.)

My front door and my back door both have regular old fashioned doorknobs which take a regular old fashioned key. No fancy computerized digital button pushing, no "smart-lock", etc...

When you come in the back door, twisting the key in the lock unlocks it, and then you come inside. If you close the door subsequently, it stays unlocked until you deliberately lock it again.

However, when you come in the front door, the key opens the door, but does not unlock it. The door remains locked until you deliberately unlock it from the inside (with the little twist-button). I feel this makes it much easier to lock yourself out of the house.

I think, but not 100% positive, that both of these locks are made by Schlage. I need to buy a new exterior doorknob, and I would like to get the kind that unlocks when you turn the key in the lock (like my current back door).

I don't even know how to ask for this at the hardware store because I don't know what those 2 different types of locks are called. I cannot seem to get any answers from internet because all I get are helpful suggestions for dealing with a lock that isn't functioning the way it is supposed to.

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    I've never heard a term for that type of lock but it doesn't mean there isn't one. I think some of those types of locks have a lever or button in the mechanism to set it either way. You might check yours. Otherwise, if you don't want to do the deadbolt as suggested by @manassehkatz-Moving 2 Codidact your best bet is to go to a hardware store and explain what you want. I know ordering on-line is more convenient but sometimes it's best to get help face to face. This is probably one of those times.
    – HoneyDo
    Jun 7, 2021 at 23:08
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    In the UK, a locksmith would call your front door locking system a "nightlatch" compared with a "deadlock" which stays locked or unlocked until you operate it. The word "nightlatch" is not commonly used except by locksmiths, and most people called them "Yale locks" from the name of a manufacturer, in the same way that vacuum cleaners are often called "hoovers".
    – alephzero
    Jun 8, 2021 at 13:51
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    @Polygnome The point of a nightlatch is that you can leave the building without a key and the door will lock again when you close it. Think about an office building where people may be working late, after the daytime security staff have gone home. You don't want to issue every employee with a key, and then hope they remember to lock the door when they leave.
    – alephzero
    Jun 8, 2021 at 14:05
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    @ilkkachu It is quite easy to open most Yale-type locks without a key. You just push back the spring-operated bolt with something like a credit card. That is actually useful, since emergency services (e.g. an ambulance crew) can enter without breaking down the door if someone inside makes an emergency call but is physically unable to get to the door.
    – alephzero
    Jun 8, 2021 at 14:08
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    @ilkkachu : OK, Yes, I'm female and not a computer programmer, so maybe some cultural/gender language issue? If you genuinely don't understand my meaning, it's like this: when you approach the locked front door from the outside, you put the key in the doorknob keyhole and turn it. This causes the doorknob itself to turn and the little latch-bolt to retract from the doorframe, allowing the door to open, even though the little twisty-button on the inside doorknob never springs out (into 'unlocked' position); so from my point of view, key opens door but does not unlock it...
    – Lorel C.
    Jun 8, 2021 at 14:29

2 Answers 2

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Lock functions (as applied to your question)

What you're discussing is called a lockset or latchset's function. There are five functions that are considered "basic" in the world of doors and hardware (entry, storeroom, classroom, passage, and privacy), but we only need to deal with two functions for this, namely entry and one of its variations, corridor (which can be seen as a hybrid of entry and privacy).

The entry function is what you have on your front door, according to this article, where you can open the door (retract the latchbolt) with the key from the outside, but need to use the inside button/knob to unlock the door, and it does not unlock when closed. What you have on your back door, though, is the corridor version, which is unlocked but not unlatched by the outside key, and has its inside handle unlocked automatically when the door is closed.

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    And my locksmith tells me “classroom” is now defunct. That meant “once unlocked it cannot be locked again without the key”. That was to keep students from prank-ing teachers by locking them out. Now post-Columbine/Sandy Hook, they reversed completely on that, but they didn’t just fit entry sets. They have big red deadbolt locks on the inside, wired to set off alarms in the office. Schools are spending a fortune on this! A student who flips the deadbolt as a prank, that’s an act of terror and they get sent straight to Guantanamo! Jun 8, 2021 at 1:30
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    @Harper-ReinstateMonica -- yeah, "classroom" got replaced by "classroom security", which allows locking from the inside with the key as well (but still permits free egress) Jun 8, 2021 at 2:01
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    @ThreePhaseEel And here's the rest of the world where the desired function of a door in case of emergency is to let everyone escape instead of not letting anyone in ... Jun 8, 2021 at 14:09
  • @HagenvonEitzen -- classroom and classroom security locksets permit free egress at all times (unlike some of the improv "lockdown" gadgets that get bandied about grey-market in parts of the US sigh) Jun 8, 2021 at 23:05
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Not an answer to the exact question, but a recommendation based on my knowledge of locks and personal experience:

The only reasonably secure locks are deadbolts.

The "doorknob locks" are nearly useless for providing real security. They are fine for bathrooms & bedrooms to prevent visitors at inappropriate times, but they are useless for preventing criminals from getting in.

Install a deadbolt on each door (front and back). Key them the same for convenience. Then either replace the doorknobs with doorknobs that do not lock at all (to avoid accidental lockouts) or disable/remove the locking mechanism.

The deadbolts should be single cylinder (key required on only the outside) in order to be safe in a fire - you don't want to have to find a key to get out of the house in an emergency.

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    @ThreePhaseEel Many years ago, I discovered a break-in at the office next to mine (and called police, etc.) Why did they pick that office? They used the key-in-knob lock and not the deadbolt. I used the deadbolt - the criminals tried that and went next door instead. Landlord did some upgrades after that to make it harder to break in, but the bottom line is that if everyone in the building used their deadbolt locks then it is quite likely the criminals would have gone elsewhere. Jun 8, 2021 at 1:12
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    It's also worth noting that most types of deadbolt are not a particularly large deterrent. They A better lock slows ingress. Thieves can be both surprisingly dumb and surprisingly ingenious. Better security gives you a larger delay and louder or more identifiable ingress, but there are many thieves who don't go to the trouble to equip themselves and can be stopped by the simplest lock, so there is value in the simplest locks. If a door has a window in or beside it, the value of increased security measures on the lock itself can be very limited unless you already have glass alams.
    – K H
    Jun 8, 2021 at 3:15
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    @manassehkatz-Moving2Codidact So real security comes not from getting a better lock on your door, but from convincing your neighbors to get worse locks on theirs. Got it. Jun 8, 2021 at 13:48
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    Two friends are in the woods, having a picnic. They spot a bear running at them. One friend gets up and starts running away from the bear. The other friend opens his backpack, takes out his running shoes, changes out of his hiking boots, and starts stretching. “Are you crazy?” the first friend shouts, looking over his shoulder as the bear closes in on his friend. “You can’t outrun a bear!” “I don’t have to outrun the bear,” said the second friend. “I only have to outrun you.” Jun 8, 2021 at 16:43
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    @KH: For any particular quality of door and frame a deadbolt will offer better security than a deadlatch, but a quality deadlatch on a quality door in a quality frame can offer better security than even the best deadbolt could offer in association with a poor quality door or a poor-quality frame.
    – supercat
    Jun 8, 2021 at 19:41

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