Using Latch Guards and Astragals to Protect Doors Against Forced Entry

Burglars have been using increasingly aggressive techniques in recent years to make forced entry into buildings. One of these techniques involves using a tool such as a screwdriver, crowbar, or prybar to force open the door. The burglar inserts the tool into the gap at the latch side of the door, and applies force to separate the door and frame. Depending on the type of lock or latch used, the door can often be opened in less than a minute.

There are three devices that are commonly-used to help prevent these types of attacks. These include the latch guard, flat astragal, and interlocking security astragal.

Latch Guard

The latch guard is a metal plate that is installed on the door adjacent to the lock set or latch. The latch guard covers the gap between the door and frame at the latch, and also extends for about 6" above and below the latch. The latch guard makes it more difficult to manipulate the latch and to force the door open in the vicinity of the latch. Latch guards are made for both in-swinging and out-swinging doors

Latch guards are relatively inexpensive (less than $50) and provide a moderate increase in security. However, it is still possible to pry open the door by inserting a tool above or below the latch guard. Also, on out-swinging doors, some burglars have been known to insert a crowbar under the edge of the latch guard itself, allowing it to be removed, or actually used as a "lever" to force open the door.

Latch Guards

Flat Astragal

The flat astragal is a single strip of metal that is installed along the edge of the door from the top to the bottom. Some flat astragals are just a simple flat bar of steel, others may be slightly curved and have weather-stripping or other features.

Flat astragals cost less than $150 and can provide a moderate level of protection if they are thick enough and properly fastened to the door. It is recommended that flat astragals be a minimum of 3/16" thick, and fastened to the door using carriage bolts spaced a maximum of 3" apart. Using flat astragals that are too thin or improperly fastened can allow them to be easily pried away from the door.

Example of Flat Astragal Pried Away From Door

Interlocking Security Astragals

The interlocking security astragal consists of two pieces, one installed on the door, and the other installed on the door frame. Both pieces extend from the top to the bottom of the door, and when the door is closed, the two pieces interlock. The interlocking security astragal is constructed of heavy-gauge metal, usually stainless steel. Interlocking security astragals are made for both in-swinging and out-swinging doors.

Interlocking security astragals are relatively expensive, usually costing $400 or more, but provide the best protection against forced entry attack.

Interlocking Security Astragal

Closing Thoughts

Any door can be forced-open if the intruder has the right tools, enough time, and sufficient motivation. The use of a latch guard or astragal, combined with other security measures, can greatly slow down an intruder, reducing the potential damage that he or she may cause. Having protective devices such as these in place may also act as a deterrent, possibly causing the intruder to move along to another easier target.

Common sense should be used when installing protective devices. For example, we have seen numerous cases where latch guards or astragals were fastened using standard screws. These could be easily removed by anyone with a screwdriver, largely defeating the purpose of installing the devices in the first place. Also, installing an expensive interlocking security astragal on a weak or badly damaged door is of little value as the door itself can be easily compromised.

If you have questions concerning the use of latch guards, astragals, or other protective devices, please contact us.

Like this article?

Visit our Security Tips page for more than 75 additional articles on a variety of topics related to physical security

Did You Know?

Silva Consultants is an independent security consulting firm and does not sell security equipment or products

Need Help?

Silva Consultants can assist you in the design and planning of an effective security program and in the selection of security products and services

Please contact us for further assistance

Thinking about becoming an independent security consultant yourself?

Buy Michael A. Silva's book on Amazon

"Becoming an Independent Security Consultant – A Practical Guide to Starting and Running a Successful Security Consulting Practice"

Published May, 2016