Apartment Key

[G-Unit]

The whole issue is to prevent someone pulling the door closed and then finding they haven't got the one and only key with them.  Your explanation does not prevent that happening, so I think you have not captured the essential part.

That isn't the issue at all, especially at the Ocean Club where other keys exist. The dead lock is an extra level of security added to the spring lock to stop people getting in.

[Robittybob1]

That isn't the issue at all, especially at the Ocean Club where other keys exist. The dead lock is an extra level of security added to the spring lock to stop people getting in.

We are not talking about the deadlock.  Both the latch and the deadlatch dropped into the striker plate.  If the moved as one they would not add any extra security.

[G-Unit]

We are not talking about the deadlock.  Both the latch and the deadlatch dropped into the striker plate.  If the moved as one they would not add any extra security.

How could they move as one? The dead lock needed a key to activate it, the other bit didn't.

[jassi]

The deadlock is not the same as the dead latch. The deadlock is in the upper part of the lock.

[Robittybob1]

How could they move as one? The dead lock needed a key to activate it, the other bit didn't.

They are both activated by the same key  first turn for the latch and deadlatch and second turn for the deadlock.

[G-Unit]

They are both activated by the same key  first turn for the latch and deadlatch and second turn for the deadlock.

You go out and close the door by pulling it to with the knob. On your return you turn the key once and get in.

You go out and close the door by pulling it to with the knob. You put the key in the lock and turn it. The door is now double-locked. On your return you turn the key twice to get in.

[Alice Purjorick]

Do you think the lower latch has been modified because I can't find an identical one on the internet? It also looks as if the upper dead bolt has been replaced at some stage as it's a different colour.

Try 6100 Series on here for a similar latch configuration. It's like that to make the latch easily reversible on installation if required.
I am baffled that lock configurations common all over the globe are suddenly full of mystique and voodoo at
37.0909° N, 8.7591° W. Is there some kind of warp there that only the truly initiated know about ?

http://www.int-door-controls.co.uk/ccp51/media/downloads/pdf/Locks-and-Latches-Brochure-07.pdf

[misty]

Try 6100 Series on here for a similar latch configuration. It's like that to make the latch easily reversible on installation if required.
I am baffled that lock configurations common all over the globe are suddenly full of mystique and voodoo at
37.0909° N, 8.7591° W. Is there some kind of warp there that only the truly initiated know about ?

http://www.int-door-controls.co.uk/ccp51/media/downloads/pdf/Locks-and-Latches-Brochure-07.pdf

Thank you. Is the mortice sash lock the nearest equivalent to 5A's?
I'm still having trouble with the physics of that rectangular piece, which appears to protrude, on the end of the  lower latch. The strike plate does not look rounded & any angling of the metal appears minimal, although the image is not the best. Having played around with some doors in my house, I still can't determine if 5A would slam shut.
Can you explain in simple terms for someone from Venus?

[Robittybob1]

You go out and close the door by pulling it to with the knob. On your return you turn the key once and get in.

You go out and close the door by pulling it to with the knob. You put the key in the lock and turn it. The door is now double-locked. On your return you turn the key twice to get in.

That would not work you can't go in and out a door repeatedly always turning the lock twice on the entry.  You would need to turn it the same number of times in both directions.

[Robittybob1]

even with a Yale lock that takes a half turn to pull the latch back the spring makes you turn the key back to the start position before you can withdraw the key.

[G-Unit]

even with a Yale lock that takes a half turn to pull the latch back the spring makes you turn the key back to the start position before you can withdraw the key.

It works just like a Yale lock if you don't double lock it. Using the dead bolt is a choice, it's not compulsory.

[Robittybob1]

It works just like a Yale lock if you don't double lock it. Using the dead bolt is a choice, it's not compulsory.

I have asked an expert for his opinion. 
I might have agreed if there wasn't that large rectangular deadlatch there as well.

[Alice Purjorick]

Thank you. Is the mortice sash lock the nearest equivalent to 5A's?
I'm still having trouble with the physics of that rectangular piece, which appears to protrude, on the end of the  lower latch. The strike plate does not look rounded & any angling of the metal appears minimal, although the image is not the best. Having played around with some doors in my house, I still can't determine if 5A would slam shut.
Can you explain in simple terms for someone from Venus?

Yup no problem. I call it "the man from Mars approach" * but it's the same sort of thing I guess.
Laters though after I have finished nailing chicken heads to the neighbours doors 

* think of how you would explain the concept of lawns to a man from Mars.

[Robittybob1]

Yup no problem. I call it "the man from Mars approach" * but it's the same sort of thing I guess.
Laters though after I have finished nailing chicken heads to the neighbours doors 

* think of how you would explain the concept of lawns to a man from Mars.

I am certain that the Martians on their many trips to the Earth have seen humans cutting what is commonly called lawn. No explanation is required.

[Alice Purjorick]

I am certain that the Martians on their many trips to the Earth have seen humans cutting what is commonly called lawn. No explanation is required.

VERY OFF TOPIC
I was thinking more of a logical explanation for the complete waste of resources.
The bit where you say "we cut it once a week in the summer"
"What do you do with the clippings then eat them?"
"Nah we throw them away".
"Hmmmm"
"What about this machine you use for cutting ; you only use it for about 18 hours a year ; do you buy one between several of you and share the expense?"
"Nah every house has one some have two"
"Hmmm"
He goes back to mother ship and falls about laughing telling his mates about the billion pound industry based on growing a bit of green stuff by your house that you cut 36 weeks in the year then throw away the clippings....