I think I've seen that knot in a book. It's a way of tying a line (half of it anyway to an object, rapelling down the GOOD half and then jerking on the other half to release the line and it all comes down.
It looks like it'd work for that. I put my short piece of heavy sprinkler line I use to simulate a railing, or whatever, between my feet, pulled on the standing end as hard as I could with both hands, and had The Admiral release it. She had to give the end a couple of pretty hard yanks, but it came free.
JUST BE CERTAIN YOU PUT YOUR WEIGHT ON THE CORRECT PIECE OF LINE!
. When this thing comes free, there's nothing wrapped around anything.
I don't have a picture handy but IIRC you start w/ a loop in the middle of your line, take it over the bar or whatever you're tying off to and then take a couple of successive bights to put tension on the line.
I'll try to describe it. Form a clockwise overhand loop where you want the hitch, with the working end to the inside. Grab the bottom of the loop, bring it under the the rail (or whatever it is to which you want to secure it), away from you, and up under the top half of the loop. Take the bight thus formed, bring it up along the standing part and take an anti-clockwise turn around the standing part. Make a bight in the w'end and pass it through that bight. Let the standing part take the load until everything is snugged-down. I can do it quite quickly, now.
I've tested it by hand, as well as I'm able, loading and unloading it, and it appears quite secure. Once it's tightened-up, it gets to a certain point and doesn't appear
to be inclined to move any more. Even under as much load as I was able to put on it by hand, it can still be released.
The rope I've been testing this with I think is Sta Set. It's pretty slippery. (It was a 5' long piece of 5/16" that was just hanging-out at the local WM that I bought for practicing knots.)