Prusik, Auto Blocks, and Klemheist Break Tests 

Check out our new store! hownot2.store/

I'm a whitewater rescue instructor and your work is gold to me!!! There is too much myth around rope and you debunk them and help making the rope sports a safer place. Love from Montréal Alex

There's no rule of only 3 wraps, that's just a starting point, when the diameter of the cord is closer to the size of the rope you need to have more wraps to create more friction. For rescue rigging a 8mm prusik is common and requires many more wraps against a single rope. The test of using 10.5mm prusik around a single 10.5mm rope will work just might need 15-20 wraps or more, haven't tried to know the exact number. Ryan should be testing how many wraps does it take to hold to be more accurate here. Also, autoblock is used with a belay device in the system, and more common around 2 ropes at the same time where there's a lot more surface area to create friction, and is more of a use case for the Hollowblock. That said, an autoblock is not intended to be directly loaded as an ascending device or progress capture. Hollowblock also comes in a longer length, probably needed for achieving more wraps when using on a single rope with friction hitches. Overall should revise the test for number of wraps needed for diameter differences to achieve the same slipping strength, number of wraps needed to achieve MBS, and comparing application of different friction hitches when using the same materials. Not trying to give Ryan more work, but think the major point of number of wraps was missed...

Adding here since I don't see this in the other comments. The Sterling Hollowblock is made from aramid fiber (hence the yellow color) and is much more heat resistant than common rope materials. This might matter in a friction hitch where things do get hot.

Ryan: Prusik knots don’t work when they’re the same diameter as the rope Blake’s Hitch: Am I a joke to you

personally i learned those three knots pretty early as i started mountain climbing, i use them as secondary safety for rappel and stuck with the prusik for purely practical reasons. prusik works both ways (which allows very comfortable details while getting in a rappel, like having it hold some slack in the rope for you), it stays on the rope even without a carabiner, and is vastly easier to get moving again after it locked tight.

Good to know I’ve been rapping on the weakest slippyest friction hitch this whole time! The thing is it works well when used for the purpose of backing up an ATC.

As a military mountaineer we are trained to use tubular webbing tied with a water knot and use that in the autoblock. I'd be curious to see the numbers on that combo.

This has been a question in my head for more than 20 years. Your guys' channel officially wins the internet. Been watching a bunch of your videos. Subscribing. Thumbs Up

Thank you how not to highline team. I've been waiting for this break test for a while. Keep up the good work.

The friction hitches are really used on arborism. But always on double rope system. If u want to use in 1 line u got to add an extra friction device. Most used are rope wrench from ISC and chicane from petzl. Anyway, the knots that u tested is not common used. If you want to try the blakes hitch, distel, michoacan will be something nice to see. I like your vids! thanks for doing its!

Rad. People been asking me this for ages. Thanks lads

in a lot of atc repells, you are wrapping 2 rope strands instead of one, I am curious if that affects breaking strength

Hello, actually it is not a fair comparison. If you read the Treeclimber's Knotbook, you will read, that the klemheist needs one more wrap, than the prusik to perform in a similar way. The autoblock (machard) needs some more wraps to be able to show its advantage. You need a longer cord and you have to make as many wraps as possible, making sure that the connecting-knot is in top of the autoblock. Than it does not slip. My results of my own tests with 6 mm cord: klemheist and prusik: 950 kg, autoblock 2400 kg (!!). Thanks for your video. Dirk from germany

Finally, i was searching so long for a video on a prusic break test 👍

I really like this channel. I work as an arborist and sherrill, which is a american dealer for arborist gear, did some tests several years ago. Their conclution was that for maximum friction the friction cord has to be 5 7ths of the climbing rope. Thanks for great entertainment.

What some may miss is the concept of fit for purpose. The Autoblock is fit for purpose when used below the device to as you say, "add friction" in an abseiling context. So in effect it doesn't need to hold all the weight, it merely needs to add enough friction so you stop if you let the Autoblock grab the rope to go hands free. Very comforting to me to see it slip and not break. As always though, test before you commit to any set up you use when abseiling or for that matter perform any transition when up in the air. Awesome set of tests. Will be using some of that data in future training sessions.

As a general note, when the ropes get wet, everything changes. The value of hollow block is that it takes higher temperatures compared to nylon. If it slips down the main rope, it will last longer than nylon will. Also, being small & sewn, with no large knot, you can attach it to a leg loop & have it be short enough to use as a third hand under a repel device that is attached directly to a belay loop

reading about knot safety and tendency to “roll” or “turn over” is not nearly as interesting or exciting as seeing that happen. 👍🏼👍🏼

Not longer than two days ago I was wondering about prussiks and thought of you guys! Awesome!

As a tree climber I use friction cord almost every day. Try and eye to eye beeline 8 mm

Holy crap. I was thinking of requesting this from you guys yesterday. You read my mind

Outstanding content - this must be the best use of RU-vid so far. Do more like this - test stuff we all do all the time! (Would also be interested in klemheist vs. viking [klemheist upside-down], but probably would enjoy your next idea just as much.)

Prusik still rules.. my camping and hammock goto. Love your channels tempo and tests (have answered most of my knot and carabiner questions I had over the over the years)

As a prusik apostle it's nice to see that I'm on the safer side while rapelling. Seeing the autoblock slipping is scary, since it has block literally in its name😅. There are also some configurations were you wind in a carabiner between the cord and the rope to use it as an ascending device. Would be nice to see them tested as well.

Super useful test for us actually working with ropes. I use my prusiks every day in my towers and masts.

I have a hollow block as a third hand (French hitch) as part of my abseiling kit. It’s comfortable to use, glides smoothly along the rope for Abseiling and can be used on different diameter ropes for different activities. the benefit of it is it’s ability to hold well on a large variety of rope Diameters without the need to carry a different diameter prusik cords. That said it is a pain in the backside to use for ascending a rope using it as a prusik (the knot becomes hard to loosen). Great videos I be learnt loads from your channel and the knowledge gain gives me confidence in the equipment Keep it up mate 👍

Nice this is definitely reassuring, thanks for the content!

Great video! I would have loved to see the VT prussik bluewater product included here because the valdotain tresse hitch is releasable under load, you can rig onto and descend a weighted rope, and the technora sheath will not melt like nylon or polyester. My guess is that the hitch will slip under a high enough load but adding wraps very effectively increases friction in my experience using it on longer rappels here in Utah.

Always watch till the end. Always bummed when it ends. Always want more.

"OK forget it it doesn't work, just like everyone says" I LOLed at that one

Really appreciate all your efforts

I use a Valdotain Tresse for ascending rope. I prefer it over mechanical ascenders!

Great video. If you ever want to stray more out of the climbing scene (similar to your recent video on rope access) and are interested in friction hitch based life support systems you should take a look at some of the equipment used by arborists. The stitch hitch, hitch hiker, rope wrench, climbing doubled rope with various hitches, etc.

Please test the Purcell Prusik, it's commonly used as an adjustable personal anchor system usually from 6mm cord and up Thank you for the content !!

Great testing & interesting results!

one of my fav videos yet!

Like you said, the closer in diameter your accessory cord to climbing rope are, so I would imagine the more likely they are to slip or fail to create a nylon saw, especially in autoblocks, as they are notorious for this for the same reason we see them consistently slip even with extra wraps. I'm intrigued to see how a Bachmann holds up to the RBS and others! Best, Isaac Also, I have a hollowblock, but it still has yet to inspire confidence, this video coaxes me to leave it at home from now on...

I mostly use the klemheist, with only two wraps, and I find that works perfectly for a smooth rappel. If I need a safety line while rigging a top rope, I use a prussik.

The advantage of hollowblock or VT prusik is that they are more RELIABLE when being used as a backup. Accessory cord does not = a good prusik. Stiffness of the cord makes them very unreliable unless they're old and fluff on an old and fluffy rope. With a designed for purpose prusik once it's wrapped the chance if it actually wanting to bite the rope is significantly better than with some random cord. The hollowblock will loose strength very quickly as it has no core, but unless it's obviously not fit for purpose it will still be strong enough to be used as a french prusik/autoblock below a descender. This is why I recommend built for purpose backups like a hollowblock or VT prusik for going down and then regular old accessory cord prusiks or slings for ascending. (All this is ehat I've observed in a decade of playing with ropes and instructing various courses)

Someone might have already mentioned this, but I use accessory cord for my prusiks while climbing and use the hollow block for kayaking. I find that the hollow block bites into ropes better when everything is soaking wet and I'm setting up Z-drags and other mechanical advantage systems in the water!

1:12 this is such a bloody greatt channel,

Thank you , order in the lab “” answered a lot of my curiosities. Great data

Thanks for these gems, Ryan! It'd be really interesting to compare water/beer knots vs their respective figure 8 counterparts (flemish bend) on tubular nylon. Nobody recommends using the figure 8, but I'd just like to see if it actually makes a difference.

Very neato, y'all! Hope you're healing up okay, Bobby!

Always amazing videos and tests... You should think next time include the VT knot or Valdotain Knot in those tests... Cheers mate...

i do most of climbing in trees. i use prusiks most the time but instead of the 3mm less rule i use 50% for biting and 70% for sliding (for instance if i were using a 10mm rope for holding me in place id prolly be using a 5 mm but if i were ascending id use a 6.5 or 7 cause it easier to break to push up the rope). the sheath/mantle also matters quite a bit based on what im trying to do and the rope characteristics, dyneema prusiks slide quite a bit more than polyester. really appreciative for your videos not all of us can have such a pretty machine.

Thanks for sharing. I love your videos !

I used a hollow block for years, or worked well, but eventually I replaced it with a sewn piece of kernmantle cord (either 5 or 6mm, I'm not sure). Kernmantle construction gives me more piece of mind, because as long as the sheath is intact, the core should be completely undamaged and also largely protected from dirt and abrasion. I mostly use the klemheist, with only two wraps, and I find that works perfectly for a smooth rappel. If I need a safety line while rigging a top rope, I use a prussik.

I tried a prusik on a 60mm smooth aluminum tube using a 10mm wide nylon webbing loop, it grabbed very well. (We were hauling a 6 meter long thick wall antenna tube up a pole, and needed something to hold it when we weren’t lifting it or trying to feed it through a clamp, not supporting a person, nobody below it if it fell etc etc).

@ 8:06 holy cow! I love this! Thanks for doing this,

I use to rock climb many many years ago carabiner and clogs and secondary rope . Times has changed so much

Fun to see, thanks guys!

This test would be nice on the test tower you’re building. To see the effect of the slippage. I use it to backup atc, to switch between shunt and atc and in case of a rappel from one bolt mid route.

Very useful , thank you very much !!!

Feel like testing a "blakeshitch"...... Great video and very informative 👍👍

Material also matters a ton! I recently switched from nylon to polyester in 6mm (PMI to Maxim brands if that matters) and the polyester is much more supple and grippy in the same length and number of wraps. I feel like polyester accessory cord might be a real win. Something else to think about!

Many years ago I used to solo climb, S roping (belay point at bottom, tie in with enough rope to reach a gear point, retie to next point, abseil back down when I run out of rope (clearing gear), then climb back up rope). Longest climbs were 3 pitcvhes. No ascender, so I used a couple of prussik loops. They worked, but it was very slow and hard work! Tried Kleimheist, but it was very hard to keep the knot 'dressed' as I slid it back up the rope. Prussik was easy to keep neat.

I like that you tried those hitches with the 10.5mm just to be thorough. Would be interesting to see how a blake's hitch would stand up to the slacksnap machine

my personal favourite way to abseil/ rappel is using a Hydrabot on a short sling to raise it up. this then gives me room to put a hollow block wrapped 3-4 times as an autoblock (french prusik). this gives me the safety of a self-belay while being able to abseil as fast as I want (hollow block is heatproof) and 1 handed for technical sections. having the belay below your repel device means it is so much easier to get going again as it doesn't have your whole body weight on it. the auto block is also super quick to tie and gives heaps of control.

This vid was particularly interesting as an arborist. We use friction hitches as life support in the form of eye to eye spliced or sewn. 8mm - 10mm Totally off your radar but I would love to see how one of our 8mm (smallest) eye to eyes holds up in your slack snap rig.

Great job 👍 thank you Sir

It would be interesting to see friction hitches on steel ropes (for zip lines, via ferrata bridges, etc). At work we sometimes use them if we forget the tensioner clamps and they always slip with slings.

I think auto bloc definitely works better for double ropes rather than single. Ive seen it slip in single ropes where a klemheist was super good enough. Thanks for the science maaaaaaaan.

ive used 5mm prusiks on 10mm rope for years even to the point of rappelling off one single prusik single rope no backup. its scary (and stupid I know) looking at dental floss holding onto your life but under static load that stuff is damn strong. Climbing rope technology is absolutely amazing.

Nice work.

I use 6 mm klemheists quite a lot in anchor building and in rappelling as well. I took a different conclusion, seems like those are pretty darn good and I still feel comfy with it.

Same diameter, try Blake's hitch! You add wraps depending on the work load, Will also lower under load... Awesome work!

This is the episode I have been waiting for!

With regards to the Sterling Hollow block product, while I've always used a 5mm cord and been fine, the sterling product just wraps up easier and is much less intrusive on the harness.

In arboriculture, I use a knot called a BLAKE. It's not only a friction knot, it's the entire rappel system. And it's made using the other end of the rope. So, you guessed it, using same diameter rope! I would not hesitate to use it in a situation where there nothing left but the rope itself

This is what I wanted to see!

Awesome! This is so interesting.

I know this is old but would love to see the Hedden knot tested like this. It’s like the klemheist pulled in the “wrong” direction (or tied “upside down”). Or similar to the RBS here but without the carabiner. Supposedly much stronger holding power than klemheist (though I was taught otherwise at my mountaineering club), definitely easier to dress.

As I watched this I was reminded of the following story from the first ascent of the Hummingbird Ridge: John Evans said ". . . it again struck me as pretty damned ultimate to start off without belay on a single strand of 1/4-inch line on a 200-foot rappel, the top 100 feet of which were free. I used a brake bar with two carabiners and fastened a Jumar to my seat sling for safety. About one-third of the way down my thumb slipped off the Jumar and it caught me and held tight. I could just barely graze the wall with one foot and could not raise my weight off the Jumar. Fortunately, I had my trusty Swiss army knife in my parka pocket so I wrapped the lower rappel rope around my body to jam it and cut the tie-off loop connecting the Jumar to my Swami. This, of course, bounced me down on my rappel brake, but I was able to grab the Jumar and release it it and finish the rappel." To which Allen Steck added "One can well share Evans' moment of intense careful thought as he chooses which of the two quarter-inch lines to cut" Ascent, Vol. 1 No. 1, May 1967 As I recalled the story while watching these tests, I had forgotten about the Jumar. I thought it was a quarter-inch goldline sling attached to a quarter-inch goldline rappel rope with a Prusik knot, but if that were the case, I guess the Prusik would had simply slipped and there would be a different tale to tell.

I always knew I didn't really ever like the auto lock for some reason 🤔The prusik was always my most trusted and favorite rappel back up...

I usually use on of Edelrid's Aramid Cord Slings to make my friction hitch, not sure if they're selling them in the US. I really love these things, they've practically replaced my dyneema slings for pretty much all purposes (lanyard, setting up a belay on multipitch, ... ) apart from in extendable draws, and I also prefer them to using accessory cord. Thing is, having a pre-tied prussic sling from accessory cord is a piece of equipment that I can't really use for anything else while I always have a few of the aramid slings on me anyway. I always prefer multi-purpose gear, plus it feels good to know that it's rated for full strength :) for the other purposes, where I use it instead of dyneema slings, it also feels more reassuring, having a sheath and all. It is heavier though.

Being drunk or as we Brits like to call "pissed". All these knots are designed to slow you death no prevent them. And the rule of thumb is, the less speed you hit something imoavble the less likely you'll die. It's not the fall that hurts, its the suden stop at the end.

Ha, all this time I thought hollowblocks were the ideal material for friction hitches. Good stuff.

I use an autoblock when rappelling regularly, and the one thing I've notices is that the knot doesn't bite unless it is shock loaded. It'll slip all day until you give it a good hard jerk. Maybe some day you can give this another try but instead of pulling straight away with the jack, you give the knot a sharp tug first so it can bite.

I’ve always heard friction knot accessories 1/2 size of main. Good reminder to pay attention to size ratings of fig 8, progressive captures, belay devices, etc

I was taught in France, that Prussik, autoblock and kleimheist knot were to be used when you have 2 strands of rope like when rappeling. On a single strand, they tend to slip. On a single strand, the knots i was shown were valdotain tresse, distel or schwabisch knot. Which are used in tree climbing.

I like using a french wrap i found for me it holds the best for me. I love your content maybe test and find the best holding wraps since there are so many options for prusiks with the same size cord? Just a suggestion keep it up Ryan

If you absolutely have to use the same diameter you can tie a Blake's hitch, works like a klemheist ie in just one direction. Using friction hitches as life support is quite standard in tree work but we use 8mm minimum cord.

Cool Video! I would suggest trying out the Bachmann hitch as well to see how it compares with the prusik.

You have to test friction hitches on the drop tower once it‘s completed. Different results there. I participated in some drop tests at a course at the Petzl Technical Institute with a dummy. We simulated a fall from a lege with some slack between the prusik and the anchor. It cut the mantle sometimes but the fall was stoppe after 30cm to 1m by the prusik.

Some thoughts: - I was taught that 4 wraps was the minimum for an autoblock or klemheist. Based on your results I definitely agree and would not ever rely on 3 wraps. - Anecdotally I've always felt that the prusik knot was the most secure friction hitch. The autoblock and klemheist trade gripping power for ease of unlocking and sliding. - I'd be interested to know what the history of that hollowblock was. The Sterling hollowblock is made from aramid fibers, which are much more susceptible to UV degradation than any of the other common synthetic fibers.

Hollow blocks are awesome!

Thanks for spelling the Prusik correctly, Ryan! 😁👍

I bootied a hollow block on a classic multi at City of Rocks, been using it since then because it was brand new. On my mammut rope I have to throw an extra wrap on my auto block because they're both pretty silky, its not a problem on our maxim. I personally would never pay 20-whatever dollars for one though. My thought would be to test the knots with 2 strands of rope inside like most people rap. Thanks for the video!

I always use 3/4 " strap and Prussik knots. They wok well and have a lot more surface area than a round cord

I tried using a hollow block the other day as a prusik to ascend a static rope (with my gri gri). It did not work at all! Any time I would weight the damn thing to pull slack through my gri gri, it would just slip! Had to switch it out and use a sling instead, which worked like a charm

8:02 That´s the most beautiful thing I´ve seen today!

I'm a member of a regional technical rescue team. We use 9mm prussics on NFPA G 1/2" static rope for almost every thing. Tandem prussic belays, progress capture, quick adjustment for anchors, anchor tie backs, adjustable fall protection, accending, holding edge pro in place, etc.

A common belaying technique in high angle rescue is a tandem prussik system. Usually 2x 8mm 3 wrap prusiks on 10mm to12mm static ropes.

Interesting, thanks

I use all of these while hunting. Saddle hunting needs alot of good knots for different uses.

Knott slippage is one of my larger questions. Seeing how they fail does seem like there are a couple variables.

i'm french and we use autoblock with 6 or 7 mm rope but we take off a bit of the inside of the rope to maje it more soft. it works fine

VT prusik!!! it's often used as a primary hold, I have repelled off one many a time (technora sheath or it burns out)