Although there may be some utopian community where people can still feel secure wihout locking doors, in most areas residents recognize the need for equipping entrance and exit doors with at least one good quality lock.

Even the best locks and security arrangements will not be enough to stop a truly determined professional burglar, but a good door lock will go a long way toward preventing a break-in in most cases.

Most burglaries are spontaneous crimes - the would-be thief moves from house to house (or apartment to apartment) looking for an easy mark - a home that will be quick and easy to enter through unprotected windows, or through doors that have locks that are easy to pick or jimmy open.

Burglars don't like noise, and they don't like delays, if one lock gives them trouble they will usually move on to another that often less resistance.

The least expensive type of door lock, and the one that also offers the least amount of security, is the spring latch lock. This is the type that has a latch bolt (the piece that goes into the opening in the door frame) with a sloping face so that the door locks when it is slammed shut. This type of latch is spring-activated; that is, the bolt is pushed out by a spring on the inside.

Although spring latch locks are convenient because they lock automatically when slammed shut, they are also the easiest to force open. When a plastic credit card or strip of metal is forced between the edge of the door and the frame it presses against the sloping face of the latch bolt to force it open.

Some spring latch locks are designed to prevent this by including a small secondary bolt, called a deadbolt, behind the primary latch. When the door is locked, this deadbolt does not fit into the opening in the strike plate. It presses against it and deadlocks the latch so it cannot be forced open easily.

For maximum protection against this type of break-in, it is better to install a separate deadbolt lock or auxiliary locking deadbolt. These are not spring-actuated. They can only be opened or closed with a key from the outside, and with either a key or a knob from the inside. Unlike the spring latch, the front face of the metal bolt is not sloping - it is squared off so that it cannot be pried open the way a spring latch can.

Some deadbolts have steel rods through the center that rotate, so that a saw blade cannot cut them (burglars sometime slide a hacksaw blade between the edge of the door and the frame, then saw through the bolt).

Auxiliary deadbolt locks come in two basic types or styles: surface-mounted locks that are installed on the inside of the door, and bored or recessed locks that fit into a recess or hole bored into the edge of the door. The better quality ones have bolts made of hardened steel that will resist cutting, and they have tapered locking rings around the cylinder on the outside to prevent burglars from prying or pulling the cylinder out of the door.

Surface-mounted auxiliary deadbolt locks are popular for apartment doors because they are less expensive than bored or recessed locks, and they are easier to install. They are also used on doors in homes, but some people object to their appearance (from the inside) when used on front doors.

Deadbolt locks also differ in how they are opened from the inside. Some have a knob to lock or unlock them; others require a key on the inside as well as on the outside. This latter type, known as a dounle cylinder lock, is recommended for doors which have glass panes, or which have glass close by. If the thieve breaks the glass, he still cannot open the lock from the inside without akey.

However, it must be remembered that in an emergency situation, such as a fire, occupants on the inside will also need a key to open the door. That is why fire experts recommend that when occupants are at home, the key should always be left in place in the lock on the inside so that the door can be unlocked quickly.

One of the strongest and most secure types of door locks is a heavy duty mortise lock. This lock is enclosed in a heavy metal case and has both a spring latch and a separate deadlatch or locking deadbolt. It is recessed (mortised) into the edge of the door and often requires double locking, that is, an extra turn of the key is required to lock it from the outside.

From the inside a separate small knob, in addition to the large doorknob, must be turned to unlock it. The newest models, however, permit unlocking from the inside with just a single turn of one large knob. This unlocks the deadbolt as well as the latch bolt to simplify exits.

Another type of entrance door lock with deadlocking features is the cylindrical lock. Not as burglar-proof or as tough as the mortise, it is easier to install and still provides better protection than a springlatch. Cylindricals usually have a keyhole in the inside knob for releasing and latching the deadbolt feature.

Most people do not realize the importance of having locks equipped with a really pick-resistant cylinder in expert burglar can pick the average lock in a matter of a minute or so, regardless of how tough the construction of the lock is. For complete protection, consumers should specify one of the various specialty cylinders which are highly pick-resistant.

Made by several different manufacturers for use in their own locks, as well as for use in other brands, these cylinders have special pin and tumbler mechanisms that are virtually pickproof. Some also use special keys that cannot be duplicated by local locksmiths or hardware stores.

No lock can be any more secure than the door on which it is installed. Make certain the door is a sturdy one that fits snugly in its frame so the frame cannot be easily pried away from the door to loosen the latchbolt. Also, the lock must be securely mounted with the proper bolts and fasteners.