Brace Your Fences Against Tests of Time : Maintenance: The proper installation and repair will protect posts and railings from decay.

Good fences not only make good neighbors, but a good-looking fence is also an asset to a home.

To make sure it withstands the wear of time and weather, it’s important to set the posts correctly and protect them from decay. After that, periodic maintenance is a good idea.

Like any wood that comes in contact with the soil, fence posts can decay. When installing a new fence, always use rot-resistant, pressure-treated lumber.

Wood posts should be set with one-third of their length, or at least 2 feet, in the ground. Here’s how:

* With a posthole digger, which you can lease from a tool-rental store, dig a hole twice the diameter of the post and flare it outward at the bottom.

* Place a flat rock or layer of gravel in the bottom of the hole and rest the post on it.

* If the post is being set in firm, well-drained soil, compact the soil around the base.

In loose soil, prepare a mixture of concrete, available prepackaged at lumberyards. Set the post and fill the hole to ground level with the concrete.

Slope it at the top so water will run off. Apply roof paint or asphalt cement to any cracks between the post and the concrete after the concrete has hardened.

* Protect the top of the post from moisture by sawing it off at an angle or by installing a metal cap available at lumberyards.

* Install steel posts the same way, but first give the lower end of each a liberal coat with asphalt paint to prevent rusting. To keep a steel post from turning in the concrete, make sure it has a flange at the base, or a crossbar passing through drilled holes.

* To give temporary support to a wobbly wooden post, drive 2-by-2 wedges on opposite sides. Bind the wedges to the post with wire.

* To avoid replacing a post that is rotted below the surface, sink a new post next to it.

Cut off the new post and bolt the two together. If the two do not touch, insert spacer block between them and wrap both with perforated metal strapping available in lumberyards. Saw the old post off at the soil line.

If a post set in concrete has rotted away at the base, chisel away all decayed wood to at least 2 inches above and 4 inches below the surface. Drive large nails into the side of the post. Make a form out of plywood, 2 inches wider than the post, to go around it. Coat the inside with oil. Prepare a batch of prepackaged concrete and pour it into the form. Tamp it down, slanting the top away from the post for drainage.

Many fence rails are simply nailed to the posts. To replace one that is splintered or rotted, just pry it off and nail on a replacement.

A rail that fits into sockets on the posts can often be repaired by splicing in a new piece. Cut out the damaged section of the rail. Cut the new piece from pressure-treated wood. At both ends of the splice, cut the new and the old pieces so that they overlap. Put waterproof glue on the joints and screw or bolt the pieces together.

If an entire rail that fits into post sockets has to be replaced, attach a new one with L-brackets. Cut off the old rail as close to the post as possible. Cut a new rail to fit snugly between the posts. Join the rail to the posts with L-brackets under each end. Caulk the seam between the rail and the post on all sides with a sealing compound.