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

Video Spotlight
Where The Wild Things Play
Where The Wild Things Play
Whipper of the Month
Weekend Whipper: Chris Sharma's 100-foot Pont d’Arc Deep Water Solo
Weekend Whipper: Chris Sharma's 100-foot Pont d’Arc Deep Water Solo

Climb Safe: How Sketchy is a Sharp-Edged Carabiner?

By Kolin Powick

The following article is courtesy of Black Diamond Equipment.


I've had several friends whip onto sharp biners with the end result being the sheathing (i.e., the sheath gets cut and exposes the core) of the rope and possibly soiling of their shorts. 

I haven't personally ever heard of a rope getting cut all the way through as the result of falling onto a sharp-edged biner, though possibly it has happened?[Note: see end of article for addendum] Regardless, we decided we'd see what it would take and set up a test in the QC lab.

We grabbed some old, sharp, worn biners that I had removed from a local sport climbing cliff, a few ropes (some new ones, some totally beat-up ones, some end sections, some middle sections (all about 10.5 mm) and went down to our trusty drop tower.



We didn't perform every single permutation and combination of possibilities, just enough to get a general idea of what would happen in certain situations. We started off using a fall factor of 0.6, 80 kg of mass and a slightly dynamic belay. If the rope didn't cut clean through on the first drop, we would continue dropping the mass on the same location of the rope until it broke. Obviously, this isn't super realistic as I'm sure if you were to take a gnarly fall and sheath your rope, hopefully you have the sense to NOT go up and fall again on the EXACT same spot on your rope.

We then upped the ante a bit by increasing the fall factor to 1, increased the mass to 100 kg and used a static belay.


Click to Zoom   


So what does all of this mean? We haven't performed nearly enough experiments to create any form of concrete conclusion, but we can make some general observations and comments, as well as decide if/what we would like to test next:

  • You can't really compare all of this data apples-to-apples since the amount of sharpness from one style of biner to another is a bit different. This can have a drastic influence on the outcome of the test.

It appears that a typical climber (~ 80 kg) in a typical fall (fall factor of 0.6 or less, using a slightly dynamic belay) onto a sharp-edged biner is unlikely to cut the rope clean through in one single fall.

However, depending on the sharpness of the biner, and type of belay, it IS possible that the rope will cut clean through on the second drop.

As expected, a higher mass with higher fall factor and static belay does result in the rope cutting earlier, in one case, with a BRAND new rope, on the FIRST DROP! (i.e., heavy climber + new rope + sharp biner + gnarly fall = CUT ROPE)

  • New biners are much more gentle on ropes than a sharp-edged biner.
  • A dynamic belay is much more gentle on ropes than a static belay.
  • Even a brand new large-radius biner (like the RockLock) can cause damage to the rope if all of the other parameters are not in your favor (e.g., old rope, static belay, gnarly fall, heavy climber).

If we were to continue along this line of experimentation, we could perform a more complete matrix of testing, changing only one variable at a time, which could possibly shed more light on which factors have the largest effect on the likelihood of the rope being damaged during a fall.



Though it is unlikely a fall onto a sharp-edged biner would cut your rope, most likely the sheath would get cut, exposing the core. However, it's always better to be more safe than sorry and swapping out old beat-up gear is a good habit to get into.

Climb safe out there,



During the testing of the rope-grooved carabiners we focused on whipping, or falling, onto the biner. I recently got an email asking about the likelihood of the rope being damaged by the sharp edge of a carabiner if it was the first biner of a route. I'm sure we've all seen fixed draws at the crags, or even at the local gym, where the first biner has been rope-grooved, resulting in a sharp edge. This is because most people belay standing back from the wall and when lowering the leader, your rope, which has picked up dirt and grit, slowly saws away at the biner. This is most prevalent on fixed first quickdraws and is a good thing to watch out for!

I hadn't heard of any accidents caused by this, but a reader from Germany just notified me that in early 2008 there was one in Prague where this exact scenario caused a new 11 mm rope to break clean through sending the climber, who was not hurt, to the ground. The report is in German, but the photo and diagram make the story clear.

So what is the moral of the story (part 2)? A sharp-edged or worn carabiner isn't only dangerous when you fall onto the biner, but can severely damage the rope anywhere in the system under the correct circumstances. As always, it's best to swap out gear that you feel is unsafe.

Be safe out there,


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.

Reader's Commentary:

Don't want to use Facebook, but still want to comment? We have you covered:

Add Your Comments to this article: