Locks and doors are your first line of defense. Most intruders enter through an existing opening. With locks, you get what you pay for. Don't scrimp when selecting locks; a few dollars up front can prevent a sizable loss. Select the best quality locks you can afford.

Accounting for every key is tantamount. If you're buying an existing home, invest in a qualified and reputable locksmith to change the locks and establish good key control from the outset.

The most secure locks are double-cylinder deadbolts, which require a key to operate from either side. The bolt (the part that extends from the door) should be at least one inch long, and should be hardened steel. The strike (the plate into which the bolt protrudes) should be installed with screws long enough to engage the structural stud behind the door frame (and not just the trim like many are installed today). A box strike (one which surrounds the bolt, not just a plate) is best.

Key-in-the doorknob locksets offer virtually no security. If your home is equipped with these, they should all be replaced.

The door should swing in to prevent any attack on the hinges. If code requires a door to swing outward, the hinges should be "pinned" (the screw is removed from opposing positions on both top and bottom hinges, and a nail is driven into one of the holes). When the door is closed, this nail engages the matching hole, and holds the door in place even if the hinge pin is removed. Any contractor can pin hinges.

Installing double-cylinder deadbolts, which require a key to open from the inside, at home (if permitted by local fire codes) is mostly a safety decision. While much more secure, they can pose a threat in the event of fire. Most law enforement officials agree that this threat can be minimized by forming the habit of inserting your key in the main entry lockset whenever anyone is home.

The safest locksets are called panic-proof deadbolts. They provide the security of a deadbolt, but open from the inside with a single action (usually a turn of the knob), preventing any entrapment in the event of an emergency. Panic-proof deadbolts can be somewhat vulnerable to manipulation from the outside if the lock is adjacent to a glass panel. Doors should be configured so that any glass panel is at least 36 inches from the inside doorknob, to prevent manipulation from the outside. Non-breakable glazing (acrylic) should be use if they must be closer than this.

Door mail slots should be removed and the hole patched, or the flap should be secured in place from the inside, so that the opening cannot be used as a means through which the lock can be reached and manipulated.

The front door should have some kind of viewer. Video door phone viewers which give a very wide field of view are available. Low cost surveillance cameras can also be used and viewed from your living room or bedroom TV.

Sliding doors are inherently less secure, and should be avoided if possible. Double-door sets, incorporating one fixed door and one working door within a sliding door-sized opening, are much more secure and give nearly equal light. If sliding doors are already in place, or must be used for some other reason, make certain the sliding panel is on the inside. You've got a serious problem if it's on the outside, because most can be lifted and removed, and almost all effective securiy devices for sliding doors rely upon the sliding portion being inside. Have a contractor install screws in the track above the sliding part so that it can't be lifted and tilted out of the frame. A "Charley-Bar" (a solid bar that latches in place between the sliding panel and the frame) can be installed in place. Most locks on sliding doors are of poor quality. Any device which latches to the frame can often be jostled out of the locked position from the outside. Request a plunger-type lock from a locksmith.

French doors, or any paired doors which don't have a center post, are inherently insecure as well and shouldn't be used on the exterior of a home. To secure an existing home with such doors, install heavy duty vertical bolts to secure the inactive leaf of the set to the threshold and to the top jam. Then install a quality deadbolt on the live leaf to secure it to the inactive one.

Auxiliary locks (a sliding piece attached by a chain to the door jam) tend to create a false sense of security and should be discouraged, as they're not effective security devices. Almost any adult can force open a door secured with only a chain. To achieve proper security, don't open your door until you're satisfied that you want to admit whomever is outside.

In summary, locks are only effective when properly installed in quality door and jam assemblies. Installing a quality lock on a chap door is pointless. And installing a lock improperly, negates almost all security value.