One fundamental concept in providing good security is known as “Concentric Circles of Protection”. This concept states that the more “layers” of protection that you provide between the outside world and your valuable assets, the better that your security will be.

One simple way to provide an additional layer of security is to lock one or more of the interior doors along the path that a criminal would need to travel to get to your most crucial assets. This can be done in both residential and commercial settings.

For example, in a private home, the master bedroom closet is one of the first places that a burglar is likely to go because of the valuable assets that are stored there. Locking the interior door to the master bedroom when the occupants are away would provide an obstacle that would slow the burglar down after entering the home. Locking the door to the master bedroom closet in addition to the door to the master bedroom would provide yet another barrier, further delaying the burglar. 

These unexpected additional layers of security may frustrate burglars who were expecting to get in and out quickly, possibly causing them to abandon their efforts and flee.

The same concept can be applied in commercial businesses by locking interior office and storage room doors. One tool supply store that was experiencing smash and grab burglaries was able to significantly reduce losses by placing high-value tools on movable displays that could be wheeled into a locked interior room after hours. Burglars who smashed through the store’s exterior windows had to locate and penetrate the locked interior room before making off with the tools.

Here are some tips for locking interior doors:

• Many interior doors, especially in private homes, are hollow-core wood doors. These provide very little security. It is recommended that hollow-core doors be replaced with either solid-core wood doors or hollow-metal doors. Preferably, these doors should not have windows within them.

• Doors should be equipped with a heavy-duty deadbolt lock with a high-security lock cylinder.

• Door and frame reinforcement kits should be used to reinforce wood doors and frames.

• Out-swinging doors that have the hinges on the outside should be equipped with security studs that prevent the removal of the door even if the hinge pins are removed.

Locked interior doors work particularly well when used in conjunction with an audible intrusion alarm system. The burglar would set off the alarm when entering the premises, and would then need to take the time to make forced entry through one or more locked interior doors while the siren was blaring, not knowing how soon the police or a security officer may arrive.

Locking interior doors is one simple, yet highly effective way to provide improved security at your home or business.