Most doors have an option where you can lock them, and then with an extra turn, you can double lock them. Does this double lock really provide some sort of extra protection? I imagine if you were to knock the door down it wouldn’t really make any difference.
The double lock, if I understand your post correctly, is a dead bolt. A dead bolt is not spring operated like the common lock in your doorknob. You’ll also notice it has a blunt rather than angled surface, which makes it much harder to jimmy. While it’s true it won’t protect much against someone determined to break the door down, it’s effective against someone who’s looking for a residence he can break into quickly.
I’m not sure I understand your answer. I’m talking about the standard type of locks on doors that you can turn once to lock them, and then turn them again to, I guess, lock them again. I have a hard time believing that the second turn involves a different physical mechanism than the first turn. The most I can see is that the bolt goes a little bit further. In any case, these kinds of locks are often found on bathroom doors, where I don’t think anyone is concerned that someone will knock the door down.
I don’t think I’ve ever seen the type of lock you describe, but maybe I’m misunderstanding you.
There are locks which have multiple “modes.” In many public buildings some doors will have both an angled latch and a deadbolt. The angled latch is depressed when the door closes, but the knob must be turned to cause the latch to retreat and open the door. In the first mode, the outside knob is prevented from moving, so the door won’t open from the outside (but can be opened from the inside and closed.) In the second mode, a seperate deadbolt is engaged which makes the door locked from both sides.
I will try to answer to the best of my ability without all the facts.
Automotive locks do from time to time come with a “double lock” feature. Mostly European vehicles and Commercial vans and trucks. The way these work, one turn will lock the door, continue turning and the vehicle is “dead locked”
A dead locked vehicle has the linkage blocked so that it becomes much more difficult to open the vehicle.
Residental locks, there is only one lock which does this on the market that I am aware of (Southern USA) It is the WeiserBolt. This looks like a standard knoblock. You turn the key to lock the latch. Continue to turn the key and the latch extends an additional 3/4 inch into the door jam.
Yes this makes a difference in a physical assult to a door. the longer the latch the more force required to kick the door in. Is the basic reason why Deadbolt locks are more secure against physical attacks than knoblocks. Of course The latch plate on the door jam must be installed correctly (use a 3 inch screw to attach to jam not a 1/2 inch screw.}
If you are refering to the internal button of the knob lock. Most commercial locks (schlage, Arrow, Sargent, LSDA) if you push the button in it shall lock the door. When the door is opened, either with a key or the internal knob, the button pops back out. If you push the button in then turn it 90 degrees, this places the lock in “storeroom” function. This will allow the door to be opened with a key or the internal knob. Yet, the button does not pop out and so the lock stays locked when the door is closed again.
If you could give me more information I can try to elaborate more for you.
Osip (the locksmith)
Posting a bit drunk this evening so pardon the typos and pissy grammar.