Sustainable Canyon Rigging: The Use of Rock V Threads
Community Note: Why We Are Sharing This Guide
Recently, several new rock V threads have been installed in some of our high-use local canyons. Because these anchors are now appearing on popular routes, accurate, practical information on how to evaluate and use them must be readily available to the canyoneering community.
As professional guides and educators, we believe in proactive safety. We want to participate in teaching the community about these specialized systems so that everyone can make safe, informed decisions when they encounter them in the field.
How to choose where to drill a V thread is beyond the scope of this essay. We just want to help people evaluate the quality of a V thread placement.
Unlinked Bolts Are The Gold Standard!
Unlinked, marine-grade 316L stainless steel bolts placed in solid bedrock are the absolute gold standard for anchoring in locations that may see water flow. They are exceptionally strong, straightforward to inspect, and have a proven safety record in the canyoning community.
Once more for the stubborn canyoners excited to get their hands on a new toy: we do not advocate for placing V threads as a universal standard. Standard unlinked bolts should remain your primary choice for bolting canyons when the rock quality is high. Instead, we present the rock V thread (derived from the classic ice-climbing Abalakov anchor) as a sustainable tool for niche situations that is worth adding to your rigging options.
Why V Threads? The Case for Sustainability and Agility
When used in appropriate locations, rock V threads are an effective way to practice long-term canyon stewardship and maintain operational flexibility.
Adapting to Features in Flux
Canyons are highly dynamic environments. Winter floods, gravel movement, and shifting logjams can alter a feature every winter. Logjams build gravel behind them, which alters how you access the edge to rappel. If the logjam blows out and the gravel goes with it, your chest-level anchor could be out in space and inaccessible next season. By adding V threads, you can simply cut the Dyneema, and there will be nothing left in the rock making the threads easy to decommission when the feature inevitably changes.
Avoiding Bolt Farms
Standard mechanical bolts do not last forever. In wet, high-flow canyons, they eventually get smashed. Removing old bolts is difficult. Over decades, popular rappel stations can become crowded with old, non-functional holes and abandoned hardware.
A rock V thread avoids this cycle of degradation. Because you are running a soft piece of cord through a clean, drilled tunnel in the bedrock, the anchor material is 100% replaceable. If the cord becomes stiff, suffers UV damage, or shows surface wear, you simply cut it out, inspect the interior rock tunnel, and thread a new cord through. The rock structure remains intact, and the same channel can be used for decades.
V Threads in Poor-Quality Rock: Quality vs. Stability
Understanding how V threads behave in poor-quality rock requires us to look at a critical paradox: the difference between rock quality and rock stability.
Why Mechanical Bolts Fail in Soft Rock
In soft, crumbly, or heavily weathered rock (such as sandstone, volcanic tuff, or soft limestone), mechanical expansion bolts can be unreliable. A wedge bolt relies on a tiny metal clip expanding against the sides of a drilled hole. Under load, this highly concentrated pressure can simply crush the soft rock surrounding the clip. The bolt then slips, spins, or pulls out entirely under minimal force.
While glue-in bolts are an excellent solution here, they require extensive preparation, carrying heavy liquid adhesive into the canyon, and waiting hours or days for the glue to cure.
How a V Thread Solves the Soft-Rock Problem
A V thread addresses this issue by completely changing the physics of the load distribution. Instead of concentrating all the force on a few millimeters of metal inside a hole, a V thread distributes the load across a large structural rock bridge (the solid mass of rock between the two drilled holes).
By utilizing 75mm or more of spacing, the cord pulls against a wide, continuous block of bedrock. This distributes the tension over a massive surface area, allowing you to establish a high-strength anchor 15-21 KN even in softer rock where a mechanical bolt would eventually fail.
Unstable VS Soft Rock
However, we must establish an absolute safety boundary: A V thread can solve the problem of soft rock, but it cannot solve the problem of unstable rock.
If you drill a V thread into a loose block, a detached flake, or an exfoliating slab, you have built an incredibly strong connection to a piece of debris. When you load that anchor, the V thread itself will not fail. Instead, the entire structural block hosting the anchor will detach from the canyon wall and fall over the cliff with you attached to it.
OK, But How Strong Are V Threads?
To ensure safety, we rely on established testing rather than guesswork. To understand the load capacity of a rock V thread, we look at the testing conducted by Grant Prattley in 2021 (Over The Edge Rescue), alongside break-test data from the Bolting Bible and How NOT 2.
What the Break Tests Show
Pratley’s slow-pull tests in hard, weathered Greywacke river boulders yielded the following results:
- The Rock Bridge: The tested V threads held six separate tests ranging from 15 to 21kN before the rock broke or the cord ruptured. This is more than sufficient to handle standard rescue or recreational loads.
- The Cord: * A 5mm Dyneema/Dyneema cord (Beal) averaged 16kn.
- A 5mm Dyneema/Dyneema cord (Aspiring) averaged 20kn.
What Materials Are Used In V Threads?
V threads are typically constructed using Dyneema cord and finished with either a rappel ring or quick link.
Dyneema Cord
- Dyneema is ideal for V threads because it is hydrophobic, meaning it absorbs virtually no water and is less likely to freeze or become stiff. It also has excellent UV resistance, high strength, and good abrasion resistance when running through drilled rock.
- Dyneema has almost no stretch and should never be shock-loaded. Dynamic falls or sudden peak loads can generate enough force to damage or break the cord.
- Identifying environmental degradation in Dyneema is beyond the scope of this guide, but HERE is an excellent study on Dyneema aging.
Rappel Ring or Quick Link
- Rings are the superior choice because of the extra clearance they provide. A ring provides a much larger internal radius, preventing the rope from binding and ensuring a smooth, reliable pull.
- A quick link’s narrow shape can easily pinch the rope.
What to Look For When Evaluating a V thread.
While V threads are a highly useful tool, they present specific technical challenges that require a disciplined approach.
To evaluate a rock V thread, you examine the two angled holes that intersect inside the rock, creating a continuous “V” shaped tunnel.
- Drill Bit: Typically, a 12mm or ½” should have been used to allow the cord to be threaded smoothly.
- Angle & Spacing: In the tested models, V threads were drilled at a 50-degree angle. Holes should be drilled to a depth of at least 75mm apart from each other and from the edge of the rock. .
- The Rock Bridge: Look for micro-fracturing, cracking, or signs of frost-wedging around and between the holes.
- The Inner Channel: Verify the tunnel is free of silt, mud, or organic debris that could hold moisture and rot the cord internally.
- The Soft Good: Check the cord for fuzziness, fading, stiffness, or signs of grit abrasion inside the fibers.
Because the critical interface between the rock and the cord is hidden inside the tunnel, you need to inspect the entire length of the Dyneema V thread to ensure that it is operational and not damaged.
Special Considerations For Evaluating V Threads
Limited Physical Space
Because a V thread consists of a cord loop resting against the rock, there is limited physical space. Clipping multiple carabiners directly into the loop can cause them to pinch against each other or the rock face. This can load the gates of the carabiners or prevent them from aligning correctly in the direction of the pull.
Triple Fisherman Required to Secure Slippery Dyneema
Dyneema is a highly slippery material. Under high or cyclic loads, standard knots like the double fisherman’s bend can slip.
- Canyoners must join the loop using a triple fisherman’s bend.
- You must pull all four strands tight to set the knot, and leave a minimum 5 to 6cm tails to prevent the knot from unraveling under load.
Specialized Tool Requirements
When opening canyons or exploring wild routes where V threads are used, you must carry:
- A specialized V thread tool (a stiff wire hook, often made from an old bicycle spoke) to reach into the intersecting chamber and pull the cord through.
- Bulk 6mm Dyneema cord to replace old loops.
Closing Thoughts: Sustainability means thinking about all community users, including future generations.
To summarize our perspective: we do not believe V threads should become the standard anchor system in our canyons. Nine times out of ten, a pair of unlinked glue-in or wedge bolts with rings is the safest, most efficient, and most reliable option for the community.
However, V threads are an incredibly valuable, low-impact tool for specific niche scenarios:
- Practicing long-term canyon stewardship by using fully replaceable soft goods instead of leaving permanent, non-functional metal hardware in the bedrock.
- Adapting to canyons in flux where seasonal gravel shifts, logjams, or dangerous hydraulics require us to adjust rappel lines dynamically.
- Managing rigging in poor-quality rock that does not accept standard mechanical bolts reliably, where a drilled V thread can leverage a larger structural rock bridge to create a high-strength anchor.
Thank you to everyone in the canyoning community for taking the time to read through this guide and prioritize safety education. We hope that having access to this hard testing data and these practical guidelines helps you feel more comfortable and confident when evaluating and trusting your safety to rock V threads in the field. Stay safe out there, and see you in the canyons!