Well Balanced Physics

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A new technique for bolted anchors

Posted on 08 Jun, 2019
Tagged highlining, inventions

The open-ended quad

There are many safe ways to attach a highline to bolts, but for a long time I’ve been dissatisfied with the style and efficiency of all the usual techniques. I've finally found a solution I'm happy with.

This concept is adapted from an anchor that Pierce Kenji showed me at Smith Rock. I got the basic idea of individually adjustable legs using a girth hitch overhand from him. His version used two sections of rope instead of four, could only attach to three bolts, and was a bit more complicated to tie. This idea also owes something to the quad anchor described in John Long’s climbing anchors book.

Here's a picture of the open-ended quad used in a rig:

The open-ended quad in action
The open-ended quad in action. The masterpoint is wrapped with a coil of tagline for edge padding

How to tie

The open-ended quad is made from four parallel strands of rope, each about 10 feet long. Near the center are two overhand knots tied about 12 inches apart, which define a masterpoint and limit extension. Two strands go to each bolt, and attach with a girth hitch overhand (defined below).

How to tie
The open-ended quad is made from four strands of rope with two extension limiting knots

Attaching to the masterpoint

The mainline and the backup can be joined to all four strands in the masterpoint by attaching the connectors like this:

Masterpoint connnection
How to attach connectors to the masterpoint of the open-ended quad. This technique keeps the connectors horizontal while attaching to all four masterpoint strands and allowing the anchor to self equalize.

Girth hitch overhand

The open-ended quad has four legs, each being a pair of strands with loose ends (hence open-ended). Each leg gets attached to a bolt using what I'm calling a girth hitch overhand knot. Here's how to tie it:

Girth hitch overhand
Pass both strands together through the bolt
Girth hitch overhand
Wrap around, so that the two ends go on opposite sides of the incoming strands
Girth hitch overhand
Tie an overhand knot with both strands. The length of the leg can be adjusted by moving the overhand knot. MAKE SURE TO LEAVE ENOUGH TAIL!


DO NOT USE A FIGURE-8 IN PLACE OF THE OVERHAND IN THE GIRTH HITCH OVERHAND! The overhand knot in the girth hitch overhand may seem overly simplistic, but this is a case where more is not better. In particular, do not be tempted to use a figure-8 instead of an overhand, which would result in a much weaker knot! See the discussion and linked test results here: https://www.climbing.com/skills/in-defense-of-the-european-death-knot/

Tie off the tails

As a final precaution, I strongly recommend tying the tails of the girth hitch overhand knot together with the tails from another bolt, using a sheet bend or a water knot. The tails from the four bolts can be tied together in two pairs as convenient. The reason for this is that overhand knot can creep and roll a few inches under very high loads. If the tails are long enough, the knot will break before the overhand rolls to the end (and the strength retention is good, see discussion below). Tying the tails together makes the whole anchor more fully closed and connected, and making sure you have enough tail to tie together also insures that you have enough tail that the overhands rolling wouldn't be an issue anyway.

Tie off the tails
The tails from each girth hitch overhand should be tied with a sheet bend or water knot to the tails from another bolt. The tails from the four bolts can be tied together in pairs

Testing the girth hitch overhand

Jerry Miszewski of Balance Community graciously performed some break tests of the girth hitch overhand knot. In three trials, he found greater than 80% strength retention compared to the minimum breaking strength (MBS) of the two strands of rope:


Why do I like the open-ended quad so much? Here's a comparison to two other commonly used anchor types. I'll be measuring each technique against these criteria:

Backed up sliding-x:

A 4-point sliding x, with individual backup connections to each bolt made with whoopie slings, 11/16” webbing, or similar.

In the normal course of events, only the sliding-x is loaded, providing a nominally equalized anchor. The individual bolt backups prevent extension and provide redundancy for the sliding-x, which otherwise is a single point of failure.



Big Effing Knot (BFK):

Start with a 4 point sliding-x, then tie a big overhand knot to create a masterpoint.



Open-ended quad:




The open-ended quad is the most elegant and easy to rig of any bolted highline anchor I've seen. I've switched to it for all of my bolted highline anchors. My only reservation about the technique is that it is possible to leave insufficient tails for the girth hitch overhand knot. Use the open-ended quad at your own risk. If it seems overly complicated to you, the BFK is still a great option.

Questions or comments? Email Ben (at) benps.com

Another anchor
Another anchor rigged with the open-ended quad, showing how the anchor is easy to set up for unusual bolt patterns