Locks, Locks, Locks, Locks

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 tumbler

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 in the US. Picking techniques developed for this mechanism were widely known and many special types were invented.

Pin tumbler

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.

Hardware differences!

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 housing. 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 50
years or more under constant use and abuse.
Grade 2 - Medium Duty Light Commercial hardware, usually designed to
last 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.

The Latch

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 side. 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 latch.

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. If 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. A 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

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.

The Rim Lock

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 security. 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 the inside.

Warning, double cylinder locks can be 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.

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