Augh, I left out a couple of things I meant to put in my first post; I got sidetracked by that story and how to share it.

I was only poking the borax about the c vs. s spellings! And yes, I see now that the split-rail fence is the much more likely reference--thanks, Dr. Bill.

I had also meant to say that fencible might not be as far off the apparent meaning as the W.A.D. seems to indicate. Even if it did mean "capable of being fenced", couldn't one reason for putting up a fence be, well, defense (or defence )?

Here's a picture of a buck fence, in case you haven't seen one of those, either.
http://www.cof.orst.edu/cof/fr/research/aspen/or_gifs/fence2.gif