My first contribution to this great forum.
I use a homemade version of these on sailboats using 1/8 spectra or vectran to replace a clevis or shackle. Spectra handles the chafe a little better than vectran, but I have a lot of 1/8" vectran on hand. Probably some good applications for ultralight folks or hammocks.
These could be used in suspension systems in place of biners, marlin spike hitches and other areas where two lines or eyes needs to be joined quickly.
These work by allowing one side of the loop to adjust opening the eye and when tension is applied the eye closes and secures the knot end. Very easy to make if you have any skills at all splicing 12 strand.
Any strong stopper knot will work on the end, I use a special knot (it's probably a lanyard knot) so that I can cut the tails very short, but it is complex knot to tie while balancing the lengths of the two "legs". A good stopper knot with a little extra tail is much simpler.
They are very strong, the applications are for racing sailboats, where weight and strength are at a premium.
I believe APS sells these as well as the Tylaska Spool Shackle, which is another great way to form a cow hitch when you don't have access to the end of the line.
MOD'S EDIT: See Post 71 for Schneiderlein's findings re: load testing the shackles:
- Use a diamond knot for loop shackles made from Amsteel.
- It is not critical to have the legs of the shackle perfectly balanced.
- The loop shackles have a failure load around 175% of the line's rating (190% for the 3mm Lash-It).
- The Ashley stopper knot and the overhand knot are not suitable for this application.