They come in all shapes and sizes and colors, different degrees of quality and with
mechanisms with different levels of sophistication. First you need to know what type of
mechanism is in your locks.
- The warded lock is the oldest type of mechanism and the easiest to
compromise. The key is of a type known as a BIT key or commonly called a SKELETON key. If
you have this type of mechanism and lose your keys, you can buy new keys at the hardware
store. They come two or three on a card and may also be called 'master keys'. This
mechanism was used regularly by the ancient Romans.
Lever locks also use a BIT key but in this case you
can't buy a ready made copy at the hardware store. Invented in 1778, it was in popular use
as new hardware until around 1900. Today it is considered almost obsolete for use as door
locking hardware and fairly difficult to get keys made for.
Invented in 1858, this mechanism is the most popular
in use in the US. It is available with varying degrees of quality with the cylinder being
made from zinc die cast metal to machined solid brass bar stock. Compromise by picking is
a well developed technique. Most high security locks available use this mechanism in
conjunction with another secondary locking mechanism.
For the last forty plus years the most popular lock
design by far has been the Key-in-knob lockset. Recently however there has been a return
to the more traditional mortise lockset, especially in commercial applications and upscale
By looking at the edge of your door and comparing to the illustrations shown
here, you can determine the specific type of hardware you have on your door. The text
accompanying the illustrations explains the operation features of each type of hardware.
Hardware comes in three basic classifications from a quality viewpoint;
Grade 1 - Heavy Duty Commercial hardware, usually designed to last 50years or more under constant use and abuse.
Grade 2 - Medium Duty Light Commercial hardware, usually designed tost
20 years or more under constant use and abuse
- Grade 3 - Residential Duty hardware, designed to last 20 years or
more under light use.
Within those classifications there are varying
degrees of quality. Some of the features to look for are listed below.
- A simple spring latch which has a bolt to hold the door shut. The
bolt will have a bevel on one side which faces the door jamb when the door is opened. The
latch can be pushed back into the door via end pressure or pressure against the beveled
This mechanism is vulnerable to attack with a celluloid strip or a credit card
forced between the door edge and door jamb. We recommend replacement with a deadlocking
The Deadlocking Latch
- The deadlocking latch resembles a latch with the exception that it
has an additional semi-circular projection at the flat side. When properly installed, this
projection remains depressed by the strike in the door jamb and effectively renders the
latch immovable. Proper installation requires that the gap between the edge of the door
and the door jamb shouldn't be more than 1/8".
You can verify that this deadlocking
finger is performing correctly by depressing it with the door open and then attempting to
depress the latch. If the latch does depress, you should purchase a new deadlocking latch
from your local hardware store or locksmith.
- A deadbolt typically does not have a bevel and requires a positive
action to throw or retract it. The throw' of a deadbolt is measured from the edge of the
door to the end of the bolt while it is extended. Pressure on the end of the bolt should
not be able to force it into the door. Typical bolt throw lengths may range from 1/2"
to over 2". The optimum is 1" or more, anything less may be capable of
compromise from prying between the door jamb and the edge of the door.
f the door jamb
does not have reinforcement between it and the stud behind it, it may be possible to pry
and bend it more than 3/4" to allow an extended bolt to slip past. Some thieves will
carry a jack for this purpose. If you do have a 1" or more extendable bolt, make sure
that the hole in the jamb is deep enough to allow it to extend fully.
You should also
mount the strike, (the metal plate the bolt enters), with screws that are at least 2
1/2" long so that they go through the jamb and into the stud behind it. This will
make it stronger than simply mounting it to the jamb and avoid the potential of kicking
force causing the bolt to break away part of the jamb and allow the door to be opened.
deadbolt is usually an auxiliary lock mounted above or below the Key-in-knob lockset but
in some cases may be interconnected with it
The mortise deadbolt is similar to the deadbolt above but is
installed in a mortise or pocket in the door. It will usually have a larger faceplate on
the edge of the door and you may be able to see one or two set screws as well. The mortise
deadbolt uses a mortise cylinder which is held in place by one of the set screws. If a set
screw is loosened it is possible to screw the cylinder out of the lock and then a finger
or other object can be used to throw or retract the bolt.
A thief will commonly try to
loosen a set screw during the day to allow him to return later and gain access. This
situation caused the invention of a mortise deadbolt with concealed set screws which the
thief can not easily loosen.
The Mortise Lockset
The mortise lockset is mounted in the same manner as the mortise
deadbolt but will usually have a latch and a deadbolt coming from the same faceplate. It
may also have a deadlocking latch and visible or concealed set screws. As with all
deadbolts, you should check to see if you have a minimum 1" throw. Some mortise
locksets will have an additional set of buttons. Pressing one button causes the other one
to pop out and the buttons are used to lock or unlock the outside knob.
If your lock has
these buttons and they don't affect the outside knob, the lock may need the spindle
adjusted or it may have an incorrect spindle installed. Older mortise locksets may have a
case, (the part inside the door), made of cast iron and one approach of the common thief
is to use force to crack the case and allow the cylinder to be removed.
While upgrading to
a stamped steel case lockset can eliminate this problem, it may necessitate refinishing
the door if the new trim doesn't cover where the old trim was mounted.
Another popular type of lock is the rim lock. It is called that
because it is mounted on the rim or surface of the door instead of within it. Typically it
should be mounted with through bolts to prevent force from pulling it off of the door and
there are versions available to do this with a pleasing finished look that also adds
The rim nightlatch is shown here while other types are available. Rim locks can
also be supplied as deadbolts or as versions whose bolt will interlock with the strike for
even more security.
The Exit Device
The exit device is a lock normally found on commercial doors and is designed to afford
easy exit in case of emergency. The exit device has an actuator which can be a paddle
shape but is usually a bar which extends 3/4 or completely across the width of the door.
Exit devices are available with alarms contained in them and some models can be wired into
your current alarm system. If your commercial building has exit devices mounted on double
doors you should have a mullion which can prevent something being slipped between the
doors to activate the exit device.
Glass Around Doors
If your lock is in a door with glass or has glass panels next to it, the lock should be at
least 40" from the glass. This will prevent a thief from breaking the glass and
operating the lock to gain entry. If the lock isn't at least 40" from any glass,
there are two options available to you;
1. Replace the glass with an unbreakable acrylic such as Lexan, or
2. Have the lock altered or replaced to require a key operation on
double cylinder locks are against codes in most cities and usually cannot be installed by
Double cylinder locks are a safety hazard in a panic
situation such as a fire and should NEVER be
locked when the building is occupied.
A locked key-in-knob lockset or mortise lock can provide good protection against illegal
entry and give you time to call emergency numbers.