On the subject of fencing (and thus getting dangerously close to being on topic) around here most fencing has wooden posts with sheep netting and a strand of barbed wire at the top, but just recently I've noticed a few being renewed with galvanised metal posts.
as far as railway fences go, a common type up here was made from old sleepers set on end with the bottom 3 feet or so buried. A horizontal strap running along about a foot from the top tied the tops together.
The tops could either be plain, pointed,
Or chamfered,
this being either on one side or both.
Another arrangement was 'castellated' where the tops of alternate sleepers were about 6" lower.
Where they ran down the slope of an embankment or cutting, the tops were stepped
I have modelled such a fence on Kirkallanmuir (third photo down the post) as they were so typical of the area.
Jim