There are two general types of doorknob assemblies, mortise-mounted and bore-mounted.

Mortise-mounted hardware relies on a large, rectangular metal box to hold its moving parts. Because of its size and shape, it has to be installed into a hand-chiseled door cavity. This type of assembly is expensive to buy and install.

At the turn of the century this was the only type of door hardware available. And although mortise-mounted hardware is still available, it is used most frequently on exterior main entry doors, sometimes in restorations. Generally speaking, mortise-mounted hardware is still the finest that money can buy.

Because of its high cost, however, its use on interior doors in modern homes has largely yielded to the easier to install and less expensive bore-mounted hardware. Bore-mounted hardware costs less because drilling two holes into the door, instead of chiseling, is used for installation. Installation is quick and easy and comparatively inexpensive.

Doorknobs fall into the "you get what you pay for" category. Less expensive doorknobs are made of inexpensive materials and are susceptible to scratches and other kinds of wear and tear. The knobs (or levers) are made of thinner and less expensive metals giving them a flimsy, tinny feel. And if the knob includes a key-lock, the less expensive ones can be opened by most amateur burglars.

If the door hardware you're considering is under $25, chances are the finish will begin to wear off in two or three years if not sooner.

There are two basic styles of bore-mounted hardware: 1) exposed mounting screw type and, 2) the concealed mounting screw type.

You can tell which type you have by looking at the escutcheon (trim ring) between the knob and the door. If you can see screw heads in one of the trim rings, you have the exposed mounting screw type. If screws are not visible, then you have the concealed mounting screw type.

In our opinion concealed-screw hardware is better than the exposed-screw style not only because it's better looking, but because more pressure can be applied to the concealed mounting plates that hold the doorknob in place. With exposed screw hardware, when screw pressure is applied to the trim plate to hold it in place, there is a chance of bending it. Leaving the screws loose enough to prevent damage to the trim plate can result in the frequent need to retighten the hardware a nuisance at best.

For less maintenance and a cleaner appearance, concealed screw doorknob assemblies are superior.

The Locking method also is an important consideration. There are two basic choices: 1) Manual relock key opens latch and changes hardware to unlock position, and 2) Auto relock key opens latch but hardware remains in locked position.

The first type must be relocked with a key or the twist of a lever each time it is unlocked with a key.

If you want a door to remain locked at all times even after you have used a key to make entry, then you want the second type. This is most frequently seen on the main entry door. With this kind of hardware the unlock mode is accomplished by a release lever or button. The key allows passage but does not control the lock-unlock function.

The auto-relock function is most common in mortise-mounted hardware, but is also available in the bore-mounted type.

A nice thing about bore-mounted hardware is most manufacturers use a universal bore. The bolt hole is usually one inch in diameter and the knob hole usually two-and-an-eighth inches in diameter. If you have one brand and want another, the bore required by both is the same.

For a new door, you'll need a one-inch drill bit, a two-and-an-eighth-inch holesaw, a chisel to recess the bolt plate and strike plate and a screwdriver to install the parts. Installing bore-mounted hardware in a new door isn't difficult and nothing could be more simple than retrofitting old with new.