Many doors offer as much protection from a determined criminal without a key as they do with one, so you could be at risk despite any other security measures you might employ. This is particularly true of outside doors that include any glass, which can easily be smashed to aid a thief's entry.

Outside doors are safest when fitted with what is called a 'five-lever mortice deadlock'. You can buy these in most DIY shops, but be sure to look at the facing plate (that's the bit in the door where the bolt pops out when the key is turned) and for extra piece of mind, you should see a 'kite mark' showing the British Standard and the words five-lever, or similar.

In some cases, your external door may not be thick enough for a five-lever mortice lock, as the recommended thickness is 44mm, if it isn't, you should look for a 'high security rim deadlock' also carrying the British Standard BS3621.

Door hinges also need to be sturdy as thieves can easily remove them. Make sure they are secured with good long screws, and for extra security fit hinge bolts to reinforce the hinge side of the door against attack.

For extra security at home, follow our advice, it may prevent you from becoming a victim of burglary:

If your front and back doors are not secure, neither is your home. Two thirds of burglars gain entry through a door.

If you are replacing a door, take the opportunity to improve your security by installing a door that is certified to British Standard PAS 24-1 ‘Doors of Enhanced Security’.

Ask for it to be fitted with a chain or bar and, if it doesn’t have a window or other means of checking who’s at the door, a door viewer.

Glass panels on or around doors are especially vulnerable, so replace them with laminated glass. Or, you can buy special film to stick to the inside that will do the same thing.

Make sure the doors and frames are strong and in good condition. Wooden doors should be solid and at least 44mm (1 ¾”) thick.

Fit five-lever mortise deadlock (kitemarked BS3621) to all outside doors, including French doors. And make sure you use them.

You can make wooden doors stronger by fitting a steel strip and plates to the door frame around the lock.

Keep your doors locked even when you’re at home. Use the mortise deadlock or, on PVC-U or other enhanced security doors, the fully or double-locked mode especially at night.

Fit mortise bolts to the top and bottom of all outside doors, including both sides of French doors.

Remember to fit all security devices with strong screws or bolts.

Before fitting locks to PVC-U or metal doors, check with the installer to make sure this will not affect your warranty.

1. Door Viewer
   If you don’t have a window in the door or some other way of checking who’s calling, fit a door viewer.
   
   
2. Hinges
   Check that the door hinges are sturdy and secured with, long screws. For added security, fit hinge bolts. These are cheap and help to reinforce the hinge side of a door against force. Hinge bolts or security hinges are especially important if our door open inwards.
   
   
3. Letterboxes
   Never hang a spare key inside the letterbox. This is an obvious place that a thief will check. Letterboxes should be at least 400mm (16 inches) from any locks. Consider fitting a letterbox cage or other restrictor, which prevents thieves from putting their hands through the letterbox and trying the latches from the inside.
   
   
4. Rim latch
   Most front doors are fitted with a rim latch, which locks automatically when the door is closed. You can open these from inside without a key. For strength and quality, look for BS3621 kitemarked products.
   
   
5. Automatic Deadlock
   This locks automatically when the door is closed and is more secure than other types of rim latch. It needs a key to open from both the inside and the outside.
   
   
6. Chains And Door Viewer
   Buy a door bar or chain and door viewer. Use them every time someone calls. Remember, though, that you only use the door chain or bar when answering the door – don’t leave it on all the time.
   
   
7. Mortise Deadlock
   Fit a five-lever mortise deadlock about a third of the way up the door. Most insurance companies are happy with one kitemaked to British Standard BS3621. You can only open a deadlock with a key, so thief can’t smash the nearby glass panel to open the door from inside. Deadlocks also mean that if burglars get into your home through a window, they can’t carry your belongings through the door.
   

Sliding Patio Doors
Sliding patio doors should have anti-lift devices and locks fitted to the top and bottom to stop them removed from outside, unless they already have a multi-locking system. Get specialist advice. If you are getting new or replacement patio doors, ask the system supplier for their high-security specification.

If you move into a new home, change front and back door locks immediately – other people may have keys that fit. Look in your phone book for the names of local locksmiths who are members of the Master Locksmiths’ Association.

Never leave your house or car keys in or near a door or window. Some thieves have been known to use a fishing rod or magnet on a stick to steal them through the letterbox.

Decide on a safe place for your keys and use it, so you can find them in an emergency.

Increasingly, burglars are breaking in to steel the keys of high-value cars. So take care of your keys and, if you have a garage, keep your car in it rather than on the drive.

If You Live In a Flat
Doors on individual flats are often not as strong as those on houses and can be the easiest way for a thief to break in.

Doors to flats over a floor level of 4.5 metres (normally those on the second floor or higher) should have locking mechanisms fitted in line with BS5588 Part 1:1990 ‘Fire Precautions in the Design and Construction and Use of Buildings’.

Shared Entrances
Consider having a phone-entry system fitted to the main door to your building. Never ‘buzz’ open for strangers or hold the door open for someone who is arriving just as you are leaving or entering the building.

Remember

• Lock – keep your doors and windows locked, even when you’re home.
• Stop – are you expecting anyone, do they have an appointment? Make sure the back door is locked – some thieves work in pairs with the other one sneaking in the back while you’re at the front door.
• Chain – put the door bar or chain on before you open the door.
• Check – check their identity carefully. Ask for an ID card. Close the door and check using a phone number from the phone book or a relevant bill, not the one on the card.

If in doubt, keep them out, particularly if you’re on your own. Ask them to make an appointment or come back later when someone else is around. Genuine callers won’t mind. If you are suspicious, report the incident to the police.

(source - Home Office)