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Personal Anchor Tethers for Climbing Safely   

Tagged in: Anchors, Belaying, Gear, Safety
by Lee Lang
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Anchors Away 

Traditionally, climbers have anchored to the belay by tying in directly with the rope. Now, many prefer the convenience of personal anchor tethers specifically designed for this purpose for belays, as well as for cleaning the top anchor on a sport climb or anchoring during multi-pitch rappels. When used properly, these systems can be safe and strong, but when used improperly, they can lead to fatal accidents.

Rock Climbing Photo: Personal anchor  by Jamie Givens

Personal anchor
by Jamie Givens
A 2007 incident on the Grand Capucin near Chamonix, France, exemplifies the danger: A climber fell less than two feet onto the Dyneema sling attaching him to his anchor; the resulting impact broke the anchor sling, and the climber fell to his death. Ledges break, climbers slip—and the result can be dynamic loading of an anchor.

All climbing cord and webbing was once made from nylon, which stretches slightly, absorbing energy. Stronger materials such as Spectra and Dyneema now allow climbers to save weight, but lack the ability to absorb energy through stretch. When used in systems with an energyabsorbing component—such as in quickdraws, where the dynamic rope clipped to the draws absorbs energy—these materials excel. When they’re used in a system with no energy-absorbing component, any dynamic event results in extremely high impact forces.

Drop tests demonstrate the danger. DMM tested an assorted batch of Dyneema and nylon slings, using a 176-pound weight in fall-factor 1 (120cm drop on 120cm sling) and fall-factor 2 (240cm drop on 120cm sling) scenarios ( Even when the Dyneema slings did not fail, the impact force (18–22+ kN) delivered to the climber likely would have resulted in massive or fatal injury.

Rigging for Rescue also tested a variety of personal lanyards and anchors, using 176-pound and 220-pound loads ( Spectra daisy chains began to fail at a fall factor of 0.25: a 220-pound weight dropped nine inches on a 36-inch daisy chain. At a fall factor of 0.5 (18-inch drop on a 36-inch daisy), virtually every daisy chain failed.

Consider the personal anchor systems that climbers are using today:

Daisy Chains 

Rock Climbing Photo: Prusik personal anchor by Jamie Givens

Prusik personal anchor
by Jamie Givens
These are aid climbers’ tools, used to link one’s harness to aiders or ascenders, but they’re commonly and improperly used as personal anchor tethers. Daisy chains should not be used as anchoring systems, for two important reasons. First, the best-case scenario for a climber dynamically loading a daisy chain is a perilously harsh impact that could break the daisy, rip the anchor, or injure the climber. Second, it is extremely easy to clip a daisy chain in such a way that you are clipped through loops that only are designed to hold body weight.

Anchor Tethers 

Specially designed tethers—such as the Metolius PAS, Blue Water Titan, and Sterling Chain Reactor—overcome a key weakness with daisy chains: the potential for improper clipping through loops. Still, most are made partly with Spectra or Dyneema (the Chain Reactor is 100 percent nylon), and none is intended to absorb much energy or withstand dynamic loading. During Rigging For Rescue’s drop tests, the PAS withstood a factor-1 fall with a 220-pound weight, but the resulting impact force was 19 kN. The potential for a factor-1 fall occurs when your waist is at the same height as the anchor and the system is completely slack.

If you use an anchor system, be aware of the risks and how to minimize them. Except for daisy chains, which were never designed to be used as personal anchors, tethers are safe, but only if they are never placed in a situation where dynamic loads could occur—the kind of load that could happen in the illustration at left. Keep the attachment weighted at all times! Even a short fall onto an anchor tether, especially if it is made of Spectra or Dyneema, can generate huge forces.I have found that it is impractical to always keep the anchor weighted, and I now use the old-school Purcell, a prusik-based lanyard that offers excellent adjustability and energy-absorption potential, with just a bit more weight and bulk than daisies. The Purcell can be purchased (from Sterling Rope) or easily tied from 6mm nylon cord. The prusik knot will slip under high load, avoiding the extreme impact forces of falls on more static tethers. At any belay stance, you can always back up your tether with the tried-and-true method of tying into at least one anchor directly with the climbing rope.

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Comments on Personal Anchor Tethers for Climbing Safely Add Comment
By Tev
From: Hickory
May 21, 2014
Wow, until now I have used the Metolius PAS system. SCARY. Will look into a Purcell or simply investing in some more 6mm cord. What length would you suggest? Also, is there a tutorial on how to appropriately tie one on? The figure pictured is a little confusing.
Thanks for your time,
By Randy Covington
Jul 14, 2014
I learned this system during training at the US army Mountain school in Vermont. I find it versatile both in sport and on mountaineering routes. Do not see it being used by many other climbers though. Great piece of gear, easy to tie and replace as needed. You probably already figured it out, but here's a link showing how its tied. Just make harness end loop long enough to girth hitch around the waist belt and leg loops on your harness, just as the belay loop is.

By rgold
From: Poughkeepsie, NY
Jan 23, 2016
Personal tethers (not daisy's, which are for aid) have a host of uses and get a lot of bad press, a lot of it from people who don't understand the range of uses of a tether and argue that you can do the same thing on the fly with slings. (You can, maybe, but not exactly the point. For example, I can do everything one can do with an ATC-XP with a hip belay and carabiner brakes for rappels. This fact has not proved to be an argument against such belay devices.)

Substituting for the rope as the anchor connection for a belayer is not an appropriate use for a personal tether---the belayer should always be anchored by the climbing rope.

Some caveats about some of the other results.

1. In the Grand Capucin accident, the real message---unfortunately obscured by the focus on the tether---is to beware of in-situ slings. No one knows whether the anchor sling would have broken anyway if the climber used a more dynamic attachment. The accident shows that bad things can happen in real situations, and are not just an artifact of extreme lab conditions, but there is no way to know whether or not a static tether was the real cause of the accident.

2. For most climbing tethering applications, the Purcell prussik is inferior to, say, a nylon chain-style personal tether, because the PP has a smaller range of adjustment and is very hard to adjust when loaded.
By JulianG
Apr 13, 2016
Petzl connect adjust solves most of the problems. If 50 bucks is too much you can get my new favorite piece of gear Kong Slyde for 8 bucks. It can used it for a personal anchor tethers or as a shock absorbent on sketchy gear while leading. I have both and I prefer the Slyde
By Seb303
From: Denver, CO
Jun 6, 2016
The Sterling Chain Reactor PAS is designed to take dynamic falls. It's price is comparable to the Metolius PAS, if not cheaper. Seems like a no brainer...
By rgold
From: Poughkeepsie, NY
Jul 17, 2016
You don't adjust PAS-style tethers by unclipping. You put a second carabiner into the primary end carabiner and then clip appropriate loops into that.

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