Traditional hauling and purchasing technique. If one end of a rope is made fast and the other is
passed around a log, say, then as you pull the free end the log rolls towards
you. In effect the log plays the part of a sheave in a block, and you get the
two-to-one purchase of a single whip. You may still see the occasional
drayman lowering a barrel into a cellar by parbuckling. A possible use for the
yachtsman is to get an inert body from the water to deck level, perhaps using a
sail in place of the rope.