A different releaseable friction hitch

   The 'RBS' hitch is obscure, but it's one of my favorites.

It has impressive holding power. It is either 'on' or 'off' with a very narrow zone between. It is the simplest possible friction hitch as far as I can tell - even quicker to tie than an autoblock. I have used quicklinks and rap rings instead of a locker, and that can work ok. The structure of the knot is basically a one-wrap heddon (upside-down klemheist) with a rigid ring at the business end instead of a soft bight. The side of the ring gets clamped against the rope in cinch mode, but the metal eyelet lets the load strand slide back easily to release it. Tie a one-wrap heddon with just 6mm cord and you will see the difference: it may or may not hold your weight, and if it does grip it won't release easily.

The 'Is the Texas rope trick safe?' thread got me to purchase a little piece of specialty hardware that creates a stiff eyelet: a stainless tube thimble for nylon rope. I tinkered with it to see what else it might be useful for. At first glance it works for the RBS hitch- but the joining knot is too big for the eyelet so that the loose ends have to be passed thru before tying the joining knot. Not ideal.

However, if I put the joining knot on the back side of the thimble, the resulting tail can become a release lever. It doesn't release as easily as a VT Prusik- I had a ~120-lb person release my ~175-lb free hanging self, but it wasn't easy for them. If you were releasing your own weight while ascending/rappelling, it would be pretty trivial since every ounce you put on the lever is an ounce removed from the load side. I used a sling hooked around my knee while hanging and did a controlled descent.

If you need more friction an additional wrap around just the rope does the trick (this is 7mm):

Since the eyelet does not flop in the same way that a ring or quicklink might, the tail can also be used to make the hitch self-tending, somewhat like a Michoacán hitch.

[I think this is pretty cool, but note: I haven't load tested it yet or worked thru potential failure modes- YMMV]         

Thimble: [      https://www.e-rigging.com/1-4-5-16-stainless-steel-tubular-thimble      ]

DMM makes thimbles for tree work that are more compact:  [      https://dmmwales.com/professional-products/rigging-anchors/thimbles      ] 

Arborists use this aramid sewn thimble Prusik loop- it might work for an RBS, but it isn't clear whether the sewn portion will fit thru the eye (Also quite pricey): [ https://bishco.com/thimble-loop/ ]