When you get to bump posts, a pile of dirt or crisscross ties would be good prior to 1950, although you can still find them today. 50 and on the western-Cullen hays taller post would be good. They was made in the 30's but too expensive most RR's didn't buy but a few each year. Seems I have an old brosure dated 1929. I am not sure of your era, most all stock pens were gone in the 70's. I seen several in Wyoming in the early 80's but they was mostly gone.