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Rev. A.3, 5/00 Page- iv
will employ the crowbar in an attempt to spread the door edge from the frame to clear the securing latch rather than
to pry the door open against the strength of the Magnalock. Electric strikes, however well made, can be
comparatively easily defeated with a crowbar by the tactic of spreading the door and this is why they should be
considered low security devices. The general fact that the Magnalock mounts on the other side of the door from the
attacker is an important contributor to its strong resistance to assault.
If the door must open in to the protected area, the attacker will have an opportunity to charge the door, kick it, or hit
it with an object. This is a less secure configuration, but Magnalocks never the less resist violent attacks of this
type. It is naturally important to use the strongest model Magnalock for the best security in this situation but the
ability of an attacker to defeat a Magnalock secured door that swings into the protected area is highly dependent on
the door type and mounting location of the lock on the door.
The key factor is that the door should be able to
give when it receives a blow, thereby absorbing the force of the blow, rather than transmitting that force to
the lock. In more technical terms, the momentum of an object striking the door will generate momentary force at
the lock as a direct function of the deceleration of the arriving object. If the object decelerates abruptly, because the
door is very stiff, it will generate a large force. Slow deceleration, as the door gives with the arriving object,
generates a relatively small force at the lock.
Once the above paragraph is understood, we can conclude that the best place to mount the Magnalock on an
inswinging door is at the top of the door/header. In fact this is best place to mount any lock on an inswinging door.
Most people prefer to mount at the middle of the door as it gives a feeling of security when one shakes the door
from the doorknob. This however is an illusion. If a strong kick is struck right at the lock, the power of the kick is
transmitted nearly directly to the lock and there is a good chance of defeating the lock or its mounting. If the lock is
at the top of the door, a kick at the door center, causes the door to flex which absorbs most of the force of the blow.
The concept of preferring a door that gives, also affects the issue of physical security on different door types. Oddly
enough the characteristics that make an inswinging door strong, can make it more difficult to lock
if it is stiff. Steel
doors and most particularly
solid steel doors such as may be found in prisons, transmit blows much more
effectively to the lock and as such may be defeated by repeated leg blows or by charging the door. If the end user
has such doors and has as well a security environment where determined attacks can be foreseen on the doors, it is
his responsibility to insure that the Magnalock's strength is adequate for the application. Selection of the model 82 is
strongly recommended with another technique being the use of multiple locks.
For critical applications on stiff doors which swing in to the protected area, Securitron offers a component that
counteracts the stiffness of the door. This is the
energy absorbing sex bolt (model EASB). Larger in diameter
than the standard sex bolt, the EASB incorporates a powerful internal spring which flexes to absorb the force of a
blow and thereby substantially increases the security of the installation.
As a final matter, be aware that the fasteners and mounting technique are just as important to successful physical
security as the strength of the lock. The fasteners must also naturally be employed on a frame area of sufficient
solidity so that it will not come loose in an attack. The Magnalock has been carefully designed to install with supplied
fasteners that substantially exceed the lock strength. If the installer replaces the factory supplied fasteners for any
reason, the success of the installation is in question. Turning to the details of Securitron's fasteners, first note the
sex bolt. This is a key component as the head of the sex bolt is the only part of the entire lock assembly that is
accessible to an attacker. Securitron's sex bolt is both large (1 1/4" dia. head) and is manufactured from steel.
Small commercially available sex bolts exist fabricated from both aluminum and brass. The use of such a component
destroys the security of the installation as the bolt head can be sheared with a chisel by an intruder.
It is also vital to mount the magnet with the supplied machine screws into the steel blind nuts. An alternate technique
is to use sheet metal screws which some installers feel is easier. This is extremely ill advised as the magnet
receives a torquing force each time the door is closed which will work the sheet metal screws free in time. We have
determined that sheet metal screws can be considered acceptable, although not preferred, if the header is made of
steel. Indeed this is mandated when Securitron's concrete header bracket is used.
On an aluminum header,
however, sheet metal screw mounting is dangerous as the steel screw threads will gradually tear through
the relatively soft aluminum.
To fully complete an installation that maximizes the effectiveness of the fasteners, Threadlock (supplied) should be
used to defend the threads against loosening over time and please refer to section 2.8 on tamper proofing for
applications where vandalism can be expected.