Determining existence of a deadlatch

[vector40]

I've been playing with mica lately, and have found that, aside from the actual technique of getting the shim into a door (which is rather harder than it seems), my main challenge is in knowning whether a particular latch is even shimmable Since I've mostly been messing with doors in my house, I can always just open it and check, but that's sort of defeating the purpose.

Does anyone know of a way to determine whether a door is deadlatched or not from the exterior, either just from external examination, or from some kind of manipulation... short of just bending a shim futilely until you give up?

[hzatorsk]

At the risk of talking 'bypass', may I offer good ways to improve the security of your doors 'against' a shim bypass.

Examine these locks closely for upgrade as they are not generally deadlatched. (It takes quality materials to successfully deadlatch.):

* Home applications (especially interior doors)
* Residental locksets.
* Home Exterior Doors (low end brands) especially when there is a seperate deadbolt.
* Clad or hollow doors set in wood jambs. (flimbsy hinges)
* Deadlatched locks that fail to engage because the deadlatch pin falls into the bolt cavity. (or can be coaxed into doing so!)
* Deadlatched doors that have shrunk significantly due to cold/dry weather, are poorly installed, misaligned... etc.
* Deadlatched doors that have their jambs spread open slightly due to warping or mechanical means.

Deadlatching is only slightly more expensive... But the door/jamb must meet accurately (which means better materials), otherwise the deadlatch will fail to engage and be worthless.

Which brings up an interesting point. If you are needing to 'test a door.... it is never wrong to attempt a shim regardless of the lock. ...after doing so, you know this door needs a locksmithing upgrade or perhaps carpenter attention.

z