The Hennessy knot comes up a lot. Looks confusing at first but it's really a pretty simple process that's repeated a few times.
I was thinking about why it exists. In all my knot books I've never come across it.
My guess is that it provides a knot that is reliable, yet can be easily untied after being put under heavy load. Otherwise why wouldn't we just tie a couple of half hitches.
What do you all think?