There are many reasons why you might need to replace a door knob. Updating a cheap builder-grade door knob to one that reflects today's trends can bring new life to something as simple as a door. Door knobs can be changed to match your home's decor. Heavily-used door knobs, such as your front door or garage entry door, take a beating over time. They can become loose or stick, making opening and closing the door more difficult.
Whatever the reason, replacing a door knob is a fairly easy job for a homeowner to tackle. The only tools you need are a screwdriver and a power drill. If your door knob has screws, simply remove them, as well as the screws holding the cover plates in place. If you don't see screws, look for a small hole on one of the knobs. Push a nail into that hole and the knob will come off. Inside, you'll see a faceplate that has screws which you will remove.
Underneath the knob and cover plate, you'll see that face plate. Again, if you're lucky, it's attached with screws that just need to be removed. If not, you'll see a slot in the plate. Use a flat head screwdriver to pop off the face plate by inserting it in the slot and twisting it. Then unscrew the latch plate on the side of the door and remove the plate along with the door latch mechanism.
Once everything is removed, you're ready to install your new door knob. They usually come with installation instructions, but the procedure is generally the same for most knobs, and it's the reverse of the way you removed the old set. Insert the new latch, making sure the curved portion faces the direction that the door closes. Fasten the latch plate with screws. Insert the new knobs into the door with the peg fitted through the opening, and be sure that the screw holes line up with the threaded cylinder on the other side. (If it's a locking knob, make sure the knob with the lock is located on the correct side of the door.) Attach the screws that hold the handle in place.
If you're replacing the door knob for an exterior entry door the process will be very similar, although you'll also have to remove the deadbolt mechanism. Again, follow the manufacturer's instructions included with your new door set.