Ascender Safety 101

       Ascending Rappel Ropes 101

       Autoblock Misuse (ATC-Guide)

       Avalanche Safety

       Belay School - Why Dynamic Matters

       Can A Hot Belay Device Melt My Slings?

       Carabiner Off-Axis and Tri/Quad-Axial Loading

       Choosing the Right Carabiner

       Common Belay Screw-ups

       Connecting Two Slings Together

       Daisy Chain Dangers

       Dangers of Rope Worn Carabiners

       Dangers of Worn Lowering Anchors

       Do Ropes Need to Rest Between Falls

       Draws in a Gym

       Extending a Cam Sling

       Fall Factors Explained

       Full Strength Haul Loops

       Gear Doesn't Last Forever—Crampons

       Gear Doesn't Last Forever—Ice Tool Picks

       Gear Doesn't Last Forever—Slings & Draws

       Girth Hitching a Stopper

       How Sketchy Is a Sharp-Edged Carabiner?

       How Strong are Himalayan Fixed Lines?

       How Strong is the Spinner Leash?

       How To Belay, Part 1

       How To Extend a Rappel Device

       Knot Passing 101

       Rappelling - Climbing's Diciest Business

       Re-Slinging Cams

       Rethinking the Double-Loop Bowline

       Retiring Old Ropes

       Sharpie for Marking the Middle of a Rope?

       Sling Strength In Three Anchor Configurations

       Spectra versus Nylon

       Spotting for Bouldering

       Surviving Bad Weather on El Cap

       The Dangers of Modifying Your Gear

       The Dangers of Short Static Falls

       The Electric Harness Acid Test

       The Skinny on Super Light Ropes

       Top Roping is Not So Safe

       To Screamer Or Not To Screamer

       Via Ferrata

       Weakness of Nose-hooked Carabiners

       What is the Safest Rappel Knot?

       Worn Belay Loops and Retiring a Harness

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Climb Safe: Sling Strength In Three Anchor Configurations

By Kolin Powick

The following article is courtesy of Black Diamond Equipment.

"What is the strongest way to rig an anchor at a belay?"

Sliding X.Now that's one of the most loaded questions I've ever heard, because, of course, there is no real definitive answer. There are so many factors involved, including quality of the placements, quality of the rock or ice, materials available, etc.

For the sake of the discussion, however, we narrowed it down to assuming two "perfect" bolt placements and using one equalized sling. My immediate answer was that such a set-up would be plenty strong for most climbing applications no matter which way you slice it, but any time you knot a sling it undoubtedly weakens it.

Remember I'm not a guide and don't pretend to be one, and I'm not suggesting which anchor equalizing method is better or worse. All I'm providing is some data based on a very few (i.e., one) data point for each scenario.



My crack crew of QA engineers and I decided to check out the three most common equalizing methods using a single 48" runner: Sliding X [not redundant], Sliding X with Knots, and Figure 8. Again, I'm not going to get into the merits or negatives of each situation (e.g., shock loading if one anchor placement blows, how "equalized" they actually are, redundancy, etc). This is just an apples-to-apples strength comparison of the three configurations.


         Configuration               Peak Load (lbf/kN )                  Failure Point            
Sliding X 8000/35.6 none (machine limit)
Sliding X with knots 4760/21.2 webbing @ knot
Figure 8 5272/23.5 webbing @ knot


Sliding X with knots.Figure 8.




















So What Do These Numbers Mean?

A couple of things to remember:

  • CE-certified slings are rated to 22 kN (4946 lbf)
  • Typical CE-certified carabiners (e.g., lockers, wiregates, bent gates, etc) in closed gate are rated 20 kN minimum (4496 lbf)
  • CE-certified cams are rated 5 kN, but most are over 10 kN

Using a Sliding X anchor, our tensile tester couldn't even break it. Now that is BURLY. And both configurations with knots were more than 20 kN in ultimate strength. So just as we've seen in previous sling-on-sling girth hitch experiments, knotting slings, etc, knots reduce the ultimate strength by anywhere from 40-60% and the failure mode is always at the knot. However, even though that seems like a big reduction in strength (which it is) the bottom line is that the anchor is still plenty strong for most any typical climbing scenario thrown at it.

Climb safe —



Kolin Powick (KP) is a mechanical engineer hailing from Calgary, Canada. He has over 20 years of experience in the engineering field and served as Black Diamond’s Director of Quality for over 11 years. He is currently their Climbing Category Director. If you have a technical question for KP, please email him at and he will TRY to respond.

To help make more climbers safer climbers, Rock and Ice has teamed up with Black Diamond Equipment to present the information here.

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