A straight, sturdy fence starts with cedar, redwood, cypress or pressure treated posts, cut close to the center of the tree. Check out the ends for an even pattern of concentric rings.
You can simply backfill your posts with gravel and earth or use metal spikes, but concrete makes a stronger, more permanent fence.
You also need: A clamshell or a power auger to dig, sturdy cardboard forms to help save concrete, gravel, some scrap 1x2s for braces and stakes… and a helpful friend.
Once you’ve checked the code, planned your fence location, had the yard swept for buried goodies like gas lines and water pipes, and staked out mason line along the outer edge of the fence, you’re ready to dig. But where?
Start at the corners. 8-feet on-center is fairly standard, but shorter fences often need closer spacing for good proportion.
Dig at least one-third the height of your post, and try and widen the hole at the bottom. Pour in a few inches of gravel and insert your cardboard form as far as the wider section.
Prepare a couple 18-inch stakes and 3 foot braces for each post. Attach one end of each brace to a stake with a single nail so it will swivel, and drive the stake in the ground about 18″ from the hole. Place the post in the hole, pour in enough concrete to help support it, and use a level on one face to determine plumb. Then firmly nail the brace to the post to hold it in place. Repeat on an adjacent face.
Then pour in your concrete, tamping it with a stick every now and then. Keep checking plumb.
At the top, slope the concrete from the post for runoff.