Choosing and Installing a Security Chain or Latch on your Door
Security chains are a good way to increase your door's security. Obviously, they can not take the place of quality entrance locks and properly installed deadbolts, but sometimes the few extra seconds it may take for a burglar to overcome them can mean everything to your survival!
Security chains were invented as a way to greet or challenge your visitors without completely opening the door, but a much better way to see outside of a windowless door is to install a door viewer or "peephole".
When installing a security chain, remember that the chain is always mounted on the stationary surface, while the slide catch is mounted on the door. The opening for the chain on the catch is located away from the door edge, making it impossible to detach when the door is open. The slide catch should be mounted close to the edge of the door. Mounting the slide catch too far from the edge of the door might make it impossible to attach/detach the chain!
Security chains are available keyed or un-keyed. Keyed security chains (as shown left) allow you to lock or unlock the chain from the outside if you're dexterous!
A sensible alternative to the classic security chain...
There are similar security devices that use a bar instead of a chain (right). They also allow you to open the door slightly but offer significantly more strength than most chains. You may have used this type of guard... they are commonly used in hotels and motels for a higher level of security and to keep the maid from opening your door while you're "sleeping". (Yawn). They also are less likely to scratch the door or frame than a swinging chain!
You should know that there is a tool (looks like a pry bar) that can open these latches from the outside. This is not a design flaw... it is so emergency personnel can get into hotel rooms without needing to break down expensive security doors. Nevertheless, I still recommend them to delay a perp's entry into your home, hopefully giving you a few extra seconds to 1) dial 911, 2) get to your gun or weapon of choice or 3) get into your safe room.
Do security chains or guards really work?
Do they work? You betcha... if you install the device properly. Follow the manufacturer's recommendations, but for extra strength you can to use longer screws than the ones provided with the kit. For example, the door frame side could use screws up to 3" to firmly attach it to the structural frame of the door. For the door side, screws with a length 1/8" to1/4" shorter than the thickness of the door will give the most strength. Also, if possible use minimum #10 screws, but it's always best to take the latch to the hardware store to get the correct screw sizing.
As a final note, pre-drill all screw holes to make installation easier and to keep your screws driving straight!