More correctly called a spring
latch or a deadlocking latch, you definitely need to know the difference.
Latches are lock bolts designed to automatically lock the door when it is pushed
Latches have one side that
is beveled and that side impacts the strike and pushes the entire bolt into the
door. Once it is aligned with the hole in the strike plate, the bolt
springs from the door to lock it in place.
The only problem with that
design is the ability to slip something like a credit card between the door and
the jamb and push the bolt back with it. A very easy defeat that doesn't
leave any sign of the unauthorized entry.
The solution to that design
problem was a guard bolt addition to the latch. When operating and
installed correctly the guard bolt prevents the latch from moving or being
depressed to unlock the door.
Operation is simple but the
adjustment is routinely incorrect unless installed by a locksmith. Here's
how you check that yours is installed and working correctly.
Only the latch bolt should
enter the hole in the strike plate. Hopefully the strike plate hasn't been
altered to allow the guard bolt to enter, only mis-located. You can use
the same tools that would be used to move the strike up or down, (see Building
Settled), to move it to the proper depth that will keep the guard bolt
depressed when the door is closed.
Don't forget to reinforce the
jamb. If you still have that air space that will allow someone to deflect
the jamb, they are effectively increasing measurement B and your door could be
vulnerable to that credit card attack.
Copyright © 2012, Thelockman LLC. ALL rights reserved