The corner posts decide whether your fence lasts twenty years

Spend your money at the corners.

That's the whole game. A fence is a tensioned system, and every pound of tension you put in the wire is trying to pull your end assemblies out of the ground. Line posts just hold the wire at the right height. If your corners hold, a mediocre fence stays tight for two decades. If they don't, the best wire money can buy will be sagging by the second summer, and you'll be re-stretching it every spring forever.

So before you price wire, price the posts you're going to anchor it to. Then double the depth you were planning to dig.

Decide what you're containing before you buy anything

Every fencing decision downstream comes from this one answer, and people get it backwards constantly. They buy what the neighbor has, or what's on sale, and then find out it doesn't suit the animal.

Cattle push and lean. They respect pain more than barriers, which is why electrified high-tensile works so well on them and why barbed wire has hung around for a century.

Horses are the expensive exception. They panic, they run into things, and a hoof through a wire mesh with a wide opening is a veterinary bill and possibly a dead animal. Horse paddocks want woven wire with openings too small for a hoof, or boards, or wide electric tape they can actually see. Barbed wire and horses is a combination experienced people avoid.

Sheep go under. Goats go over, through, and occasionally around in ways that will make you question your career choices. Both want woven wire with tight spacing at the bottom, and goats want a hot wire on top as well.

Write the answer down. If you might run something different in five years, build for the harder animal now. Adding a fence later costs more than over-building once.

Walk the line, twice

Before a single post goes in, walk the whole perimeter with a bundle of flagging tape.

Look for low spots where water runs. A fence crossing a gully will collect debris in the first big rain, and debris is a sail that pulls the whole run down. You either need a floodgate section there, or you route around it.

Look for rock. Look for trees you'd have to fight, and stumps you'd have to fight harder. Look for where your tractor and trailer will actually need to get through, because that's where a gate goes, and gates want flat, dry ground.

If your boundary line isn't pinned and obvious, stop. A fence built eighteen inches onto a neighbor's ground is a lawsuit waiting for a bad mood. Get a surveyor to mark it, and talk to a property attorney if there's any history of disagreement. That cost is trivial next to moving a finished fence.

Then call your utility locate service before you dig anything. Free, legally required in most places, and the alternative is hitting a gas line with a post driver.

Building an end assembly that doesn't move

The standard is the H-brace, and it's standard because it works.

You want a corner or end post that's substantial — commonly eight inches or more in diameter for a serious livestock fence — set deep. Three and a half to four feet in the ground is a typical target, and deeper in sandy or wet soil. The post should go below your frost line, not just near it.

The brace post sits alongside, usually set so the horizontal rail between them is roughly twice the height of the fence. Too short a brace and the whole assembly levers out of the ground. That's the single most common amateur mistake, and you can spot it from the road: a leaning corner with a stubby little brace beside it.

Run a diagonal brace wire from the bottom of the end post to the top of the brace post, then twist it tight with a stick or a proper twitch. Double-wrapped is better than single. That wire is doing the actual work of transferring load into the ground.

On dirt, tamp in layers. Six inches of backfill, tamp hard, repeat. A properly tamped post in good soil often outlasts a concreted one, because concrete in wet ground can hold water against the wood and rot it at the collar. If you do use concrete, crown it so water sheds away.

Corners take the pull from two directions, so they need bracing in both.

Line posts, spacing, and the honest trade-off

With high-tensile wire, line posts can go twelve to sixteen feet apart because the wire itself carries the load. With woven wire, you want them closer — commonly eight to twelve feet — because the fabric needs support.

Driven posts hold better than dug-and-backfilled posts. A hydraulic driver on a tractor is worth renting for a day even if you only have a hundred posts, because the ground is compacted around the post instead of loosened.

Steel T-posts are cheaper and faster than wood. They also bend when a cow leans on them and they're a genuine hazard to horses unless capped. A reasonable compromise on a long run is wood every fifth or sixth post with steel between.

On hills, remember the fence has to be pinned down as well as up. Wire wants to lift at the bottom of a dip, so you'll need a post anchored against upward pull there, sometimes with a deadman or a tie-down.

Gates, and where people waste money

Put gates in the corners of a paddock, not the middle of a run. Livestock naturally travel along a fence line into the corner, and a corner gate uses that instead of fighting it.

Hang the gate off a dedicated gate post with its own brace, not off the corner post that's already taking the strain of two fence lines. Gate posts carry a swinging cantilevered load all day, every day, and they want to be the biggest post on the property.

Go wider than you think. Twelve feet is a minimum for a tractor with an implement. Sixteen is better. The cost difference between a twelve and a sixteen foot gate is small. The cost of dismantling a fence panel every hay season for twenty years isn't.

Tension and the first year

Stretch high-tensile in stages and let it sit. Wire stretches, posts settle, ground moves. Build in-line strainers so you can retension without dismantling anything.

Then walk the whole fence at the end of the first winter. Snap a few staples back, tighten the strainers, look at every end assembly for lean. Frost heave shows up in year one, and year one is when it's cheap to fix.

Staple wood posts loosely enough that the wire can slide a little through the staple. A staple driven flat and hard pins the wire, and pinned wire snaps at the post instead of moving.

What it actually costs you

Materials for a proper fence are maybe a third of the job. The rest is labor, and labor is you, and you're slower than you think.

Budget a full day per good end assembly if you're doing it by hand in hard ground. Budget for the post driver rental, the wire spinner, the come-along or chain strainer, the fencing pliers you'll leave in the grass and have to buy again.

And budget the truth: fencing is the least glamorous work on any property and the work that most determines whether the rest of it functions. You won't enjoy the day you build the corners. You'll enjoy every year afterward when nothing gets out.

Go dig deeper than you want to. That's the job.