A burglar alarm system is the best device for detection of a burglary in progress. It is for this reason that burglars stay away from homes and businesses that are equipped with a burglar alarm system. A well-designed system will provide detection of the common techniques used by burglars.
#1 – Slip-Knifing
Probably one of the simplest attack techniques is slip-knifing. A thin, flat, and flexible object, such as a credit card, is inserted between the strike and the latch bolt to depress the latch bolt and release it from the strike. Slip-knifing of sliding windows is accomplished by inserting a thin and stiff blade between the meeting rail (stile) to move the latch to the open position; slip-knifing of pivoting windows is done by inserting a thin and stiff wire through openings between the rail and the frame and manipulating the sash operator.
#2 – Springing the Door
Springing the door is a technique in which a large screwdriver or crowbar is placed between the door and the door frame so that the bolt extending from the lock into the bolt receptacle is pried out, enabling the door to swing open. A 1-inch bolt will hinder this attack.
#3 – Jamb Peeling
Jamb peeling is the prying off or peeling back the door frame at a point close to the bolt receptacle. When enough of the jamb is removed from the receptacle, the receptacle can be broken apart or removed, allowing the door to swing open. A metal or reinforced door frame is the antidote.
#4 – Sawing the Bolt
Sawing the bolt is inserting a hacksaw blade between the door and the door frame and cutting through the bolt. The countermeasure is to use a bolt made of a saw-resistant alloy or a bolt that is seated in such a way that it will freely spin on its side, thereby taking away the resistance needed for the saw blade to gain purchase.
#5 – Spreading the Frame
Spreading the frame involves the use of a jack, such as an automobile jack, in such a way that the door jambs on each side of the door are pressured apart to a point where the door will swing free from the bolt receptacle. A reinforced door frame and a long deadbolt are countermeasures.
#6 – Kicking in the Door
Kicking in the door is a primitive, but effective technique. In this case, the attack is against the door so that even the best locking hardware will have little deterrent effect. The countermeasure is a metal door or a solid wood door, at least 1-3/4-inches thick, installed in a wooden door frame at least 2-inches thick, or a steel door frame. An escutcheon plate can be used to shield the bolt receptacle.
#7- Picking the Lock
A more sophisticated attack technique is lockpicking. It is seen infrequently because of the expertise required. Lock picking is accomplished by using metal picks to align the pins in the cylinder as a key would to release the lock. The greater the number of pins, the more difficult it is to align them. A cylinder should have at least six pins to be resistive to lock picking.
#8 – Manipulation of Combination Locks
The high-security form of the combination lock requires manipulation of one or several numbered dials to gain access. Combination locks usually have three or four dials that must be aligned in the correct order for entrance. Because only a limited number of people will be informed of the combination, the problems associated with compromised mechanical keys and lock picking are removed. Combination locks are used at doors and on safes, bank vaults, and high-security filing cabinets; in most cases, the combination can be changed by the owner on an as-needed basis.
With older combination locks, skillful burglars may be able, often with the aid of a stethoscope, to discern the combination by listening to the locking mechanism while the dial is being turned. Another attack method is for the burglar to take a concealed position at a distance from the lock and with binoculars or a telescope observe the combination sequence when the lock is opened.
The combination padlock has mostly low security applications. It has a numbered dial and may be supplemented with a keyway. On some models, a serial number impressed on the lock by the manufacturer will allow the combination to be determined by cross-checking against a reference manual provided by the manufacturer to dealers. Although a convenience, it is a risk to security.
#9 – Padlock Substitution
In a technique called padlock substitution, the thief will remove the property owner’s unlocked padlock and replace it with a similar padlock. After the property owner locks up and leaves, the thief will return, open the padlock and gain entry. The preventive measure is to keep padlocks locked even when not in use.