The key to guard rail installation is getting the posts in the right spot to line up with the standard pre-punched mounting holes in the rail....   I found that out the hard way. Put in RR tie posts on 8 ft centers for boards. Gave up on boards and went to guardrail. Rail would have been MUCH easier with RR ties on the std 6'-3" (who ever came up with that # I wonder) guard rail hole spacing.

When installed I don't think the guardrail looks too bad. 

I also used scrapped old telephone pole posts with old 2 x 10 saw mill reject oak boards for much of my corral.

Jim at Dawn