Bill when I was on the farm we used them all of the time for our hogs. We would dump in used motor oil and the pigs seemed to love it. They were always scratching. Years later we found out that probably the reason they were scratching all of the time is because the oil we used was harsh to the skin. They probably scratched because the were hurting. Much like when people have a rash all they can seem to do is scratch. I really felt sorry we were causing more pain than relief. Most of ours had almost round metal blocks that you would slide over a small cable and the oil would drip on the cable from the top. It would seep out between the blocks. OOOOOOOOO for the good ole days.