Evan wrote:

As to the issue of double cylinder locks used on residential doors
in homes without sprinkler protection:

It is against the national building code to have double cylinder locks
installed on any egress door in a residential building... So those
who
have such locks installed on EVERY door in their homes are clearly
in violation...

Last I heard there were several building codes.

I have the equivalent of a key-in-knob lock and a double cylinder
deadbolt on outside doors. The double cylinder locks on the main door
are only locked if everyone leaves the house.


Since most burglars are not lock pickers and will use brute force to
open doors (even those with deadbolts installed on them) having
such double cylinder equipped locks provides no additional protection
since the opening that is breached will allow removal of items from
inside the home...

Two locks create more areas that have to fail to get through the door.
The strikes are steel plate with long screws into the studs.

Burglars can remove what they take through the window they broke in through.

Hinge pins can be removed from other doors to
provide exit if it is equipped with a double cylinder deadbolt if you
have some extraordinarily valuable item which is unable to be carried
off through the point of entry...

The main door has pins between the hinge halves. There are several ways
to prevent defeat from hinge pin removal. I really doubt many burglars
are going to remove hinge pins to get out of a house.

The lock cylinders screw into the mortise lock, and can not be removed
without opening the door.


So since double cylinder locks do not provide any additional
protection
compared to a single cylinder lock,

They do on my house.

A lot of security is making your house a less attractive target than others.

what do they actually provide:

Both irrelevant.

--
bud--