Fence boards on a hill ? how to level to the road/land or true level?

[Charlesaf3]

whether it splits depends on wood - dry hardwood near ends I'd predrill for screws. But I'd bet good galvy gun nails will last fine in your application - I'd hook up the hitachi and go to it. I'd use ring nails in the framing gun myself. Shouldn't split if you use a little caution, ie back from the edges angled in.

How far up from ground is a looks question. tack a section up, step back, and see what you think (carpenters tack - ie one nail so its easy to rip. A brad or 2 would probably hold fine temporarily). 14" sounds good off hand. I'd keep the distance between rails constant though, and wouldn't vary them way off the initial.

I forget what a ring holds in shear, but waaaaay more than you'll need. Put 2 in each end to my mind and you'll be fine.

A big tractor plus auger is a good thing And will be better once I get the QA ears to mount it on the end of the backhoe

 

[sld]

I would make a couple of spacers out of 2x4's that you can set on the ground next to each post. This will set the height of the bottom board. Then put the spacers on the bottom board (quick clamps?) and nail the middle set. Do the same for the top. If you use these same spacers everywhere, all the rails will be very uniform plus it beats measuring each one.

 

[SuperDuty335]

Board rail fencing should run with the contour of the land. With that said, make sure the distance between posts are measured on the slope and not on horizontal.
Edit:
I should have read more carefully about the posts being there. (My advice is still accurate if you need to set new posts) The way you marked the posts is also accurate. The boards will be the same distance off the ground, just not level along the hill. Are you in NC? I work all over the foothills and piedmont.

 

[Blueridgecabin]

Thanks to all that have help me so far
What size nails do I use ? I called the rental stores for a nail gun and all they have is they type to nail plywood and use "8penny nails".
If I use screws What size galvinized ones?
I am afraid of knocking my post off plumb, I drypacked them and we have had some rain here but not a whole lot.
My boards come tomorrow.
I like the idea of making spacer boards to keep them even.

Blueridgecabin

 

[jimgerken]

It might be too late for this first advice, but here goes anyway. If the ground is very irregular, do yourself a big favor before building fence and run a boxblade or better yet a hired cat down the entire fenceline to make the irregularities more gradual. You will save much time by following gradual changes. And you will be glad that there are no weeds or small trees in the way either, after the cat pass.
Nail gun advice: When nailing wood that is very hard, and maybe already dry, so tends to split, it helps a lot if you blunt the nails. Assuming the nailgun nails are in a line, not glued or papered together in a stairstep pattern like some, take the nail line and carefully run the points on the belt sander to blunt them. It doesnt take much, maybe take off 0.025" back from the sharp point. Then the way they work is they tear thru the wood a bit, punching a hole instead of splitting between fibers. This works excellent on hardwood casing and trim inside your house, I assume it would be just as effective on outside wood projects.
Good luck!