Dear dnes: My hat off,and an effort at deep bow (frustrated by my ankylosind spodylitis_) using your clues, I found:
Parbuckle
(Par"buc`kle) n. (a) A kind of purchase for hoisting or lowering a cylindrical burden, as a cask. The middle of a long rope is made fast aloft, and both parts are looped around the object, which rests in the loops, and rolls in them as the ends are hauled up or payed out. (b) A double sling made of a single rope, for slinging a cask, gun, etc.

I never heard of it before.