Sometimes when clipping in people who are rappelling, or setting up anchors in some places from above or showing people how to get onto a fixed line, I need an adjustable tether.

I often carry a nylon cordelette for just such a purpose, what knot should I use?

  • 1
    Wow, the purcell prusik looks horribly over-engineered to me. Why not simply use a sewn sling and adjust the length e.g. with a clove hitch? – anderas Aug 16 '18 at 20:38
  • @anderas For my use case, that wouldn't be long enough and the prusik slides really nicely with just one hand to adjust – Charlie Brumbaugh Aug 16 '18 at 20:42
  • Daisy chain and fifi hook? One-handed operation, quick and easy, adjustable to within 5cm typically. – Beanluc Aug 16 '18 at 23:15

The solution to this is a Purcell Prussik, that looks like this,

Purcell Prussi

It's a cordelette tied into a loop with a double fisherman's, and then looped back with a prussik to itself. See here for how to tie one.

If I need more slack, I reach up and pull the prussik towards myself, if I need to go shorter I push it up towards the anchor.

It is important that the loop with two strands goes to the climber, as otherwise, you **** without climbing back to the anchor when it is fully extended.

The other thing to note is that the double fishermans won't go through the prussik, so you want it as close to the side that goes to the anchor as possible but not directly on it.

Finally note that this should only be used with a cordelette made out of nylon cord and will not work with a cordelette made from dyspectra/dyneema or a webbing as it will likely slip.

If you need to shorten one, you can tie a figure eight on bight on the part of the cordelette that goes to the anchor and clip the bight to the anchor.

Close up of the prusik,

Purcell Prussi

  • Is there a nice way to attach the Purcell to two anchor bolts without creating an American death triangle? I've always wondered how people who use the Purcell as their personal protection deal with this issue. – Qudit Aug 16 '18 at 18:19
  • @Qudit See the picture at the top, you clip the locking biner to the master point. – Charlie Brumbaugh Aug 16 '18 at 18:21
  • That's fine after the anchor is set up, but what about when cleaning? There is no master point then. – Qudit Aug 16 '18 at 18:22
  • @Qudit I have only ever used it where I expect it to hold my body weight, so clipping to just one anchor bolt is an acceptable risk in my opinion. – Charlie Brumbaugh Aug 16 '18 at 20:03

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