PropTech Corner
By David Trepp
How Anti-shim Pins Secure Door
Locks (Or Not)
We all use, and trust, door locks on a daily basis. Our homes,
offices and commercial real estate holdings are all protected
by door locks, and these locks are surprisingly sophisticated
devices. This sophistication is a result of the need to combine
security with ease-of-use. Unfortunately, this sophistication
also brings with it the need to carefully install locks, or they
may not function as intended.
The most common door lock includes a handle, a key
mechanism, a latch plate with a hole in it and a latch with
an anti-shim pin. In future articles, we will explore how door
handles and key mechanisms can be exploited. For this
edition’s article, we are going to focus on perhaps the most
overlooked, and essential part of the lock, the anti-shim pin,
a.k.a. the dead latch.
The anti-shim pin/deadlatch is the narrow, half-cylinder
piece that sets next to the door latch. The anti-shim pin’s role
is to prevent the lock from being susceptible to shimming.
Shimming is often referred to as the credit-card trick,
wherein the criminal uses a credit card (or similarly semi-
flexible piece of plastic), to depress the door the latch and
open a locked door.
When the door is closed, the latch passes through the hole in
the strike plate, but the anti-shim pin should be resting on the
face of the strike plate in its retracted position. It is essential
the anti-shim pin remain in its retracted position in order to
prevent shimming.
In our security test engagements, we often find deadlatches
are either mis-aligned during installation or door alignments
have changed over time due to things like the building
settling or rubber doorframe bumpers decaying. When
mis-installation or building changes occur, the deadlatch
often ends up extended (like in the picture above), which
renders it useless.
If you want to prohibit easy physical attacks against your
properties, pay close attention to door alignment and make
sure all you anti-shim pins are in the proper retracted position
when doors are closed. n
David Trepp is a Partner in BPM’s Information Security
Assessment Services Practice. Contact David at
[email protected] or 541-687-5222.
14 BPM Real Estate Insights
The anti-shim must be depressed
when the door is closed to be
properly secured