A doorknob is one of the simplest mechanical components in the home and one of the most useful.

Unless you live in a custom or semi-custom home, the door hardware is most likely "vintage subdivision" or "builders basic." Changing a lockset is one of the most cost effective and user-friendly do-it-yourself projects that a home owner can tackle.

There is some information that you'll need before heading out to your local home improvement center for new door hardware, including the bore and the backset. The bore is the diameter of the hole through which the lockset's cylinder is installed. While bore size can vary as much as hardware style, 2 1/8 inches is among the most popular. This can be determined by measuring the diameter of the bore once the old hardware is removed. The backset is the distance from the center of the bore to the face edge of the door. Here, too, the combinations are almost infinite, with 2 3/8 inches being among the most common. The backset is the space required for the latch assembly to attach to the cylinder. It typically consists of a bore of about an inch, into which the latch assembly is inserted.

The final element that will influence the lockset's fit is the size and configuration of the faceplate that is attached to the latch assembly. It is through two holes in the faceplate that screws are inserted to fasten the latch assembly to the door. Some faceplates have square corners while others have rounded ones. In either case, be prepared to do a bit of mortising with a sharp chisel or some patching with a wood dough or vinyl spackling compound. This process might also need to be undertaken when installing a new strike plate at the door jamb.

A word about replacement hardware. If you are taking the trouble to replace the hardware, don't be cheap! Choose a style that will not only dress up your home, but will operate smoothly and offer lasting quality, as well. A brand-name product with a medium price is a good place to begin. The more expensive the hardware, the better the finish and mechanical components.

With new hardware in hand, the replacement process is simple. Aside from the chisel mentioned earlier, you'll need a small hammer and a couple of screwdrivers a flat blade and a Phillips head.

Remove the existing hardware by inserting a flat-bladed screwdriver into the slot on the shank of the interior doorknob. The decorative trim plate or "rose" can be pried off with a screwdriver or unscrewed, depending upon the model. Next, unscrew and remove the mounting plate which is immediately under the rose. This will allow for the removal of the exterior knob and cylinder. Unscrew and remove the faceplate, latch assembly and strike plate. The door should now be completely free of hardware. The new hardware can now be installed. One side note: If you are considering painting the door, now would be the time to do it. The new hardware should be installed after the door is painted to make painting easier and to avoid dripping paint on the new finish.

The new lockset is installed essentially as the old hardware was removed, except in reverse order. Insert and screw on the new latch assembly and faceplate. Holding the exterior knob and cylinder, slide the cylinder in and engage it with the latch assembly.

Attach the mounting plate and snap on the interior rose and knob. Screw on the new strike plate, and check that the latch engages into it. Adjust the strike plate as needed for a solid connection.