A sheepshank, is that the same as what some call a truckers hitch?

No. The trucker's hitch (lots of neat info on that just discevered site...) is something completely different from a sheepshank.

The sheepshank sounds like what Bitt wants. Add the second half hitch, and it may work for your application, even though it's not under constant tension. At least it seems to work in my test rope.