Today we are going to analyze whether installing webbing into an Alpine WebLock 4, 5, or 6 fully upside-down has any effect on the holding power or strength of the webbing in the device.

When we say Upside-down, we mean the weblock is oriented upside down and the webbing is installed right-side up, resulting in a very wrong installation, according to the way it is meant to be used.


In order to look at strength retention values, we need a baseline strength for every slackline webbing we test (Control Group). In order to do this, we have opted to follow the guidelines of the ISA with how they test slackline webbing in order to be ISA certified. They use a device called the "Whale", which is a webbing anchor with an 80mm diverter and no webbing overlap on the first bend. We built our own version of this device, dubbed the "Blue Whale", and used it on every webbing we tested. Our version requires a sewn loop on each end of the webbing we test, which is anchored to a grade 9 bolt going through the Blue Whale.

Blue Whale

The webbing wraps around the Blue Whale main diverter, around the center bolt, and then back up to the back bolt, where the sewn loop is anchored. Each side of the sample wraps around the main diverter in the opposite direction, giving an even loading through the thickness of the webbing.

Each sample starts as a 6.5 foot (roughly 2 meters) piece, then a 5.5 inch (14 cm) length is folded over on each end and a sewn loop is added. The final sample length is then 5 ft 7 inches (170 cm). We have learned throughout these tests that long samples are a necessity. We get drastically more variance with short samples.

Each webbing tested has at least 4 samples, and up to 8 samples done. The 4 sample types were done because we ran out of material.

After having a Control Group to test against, we ran our test samples. This includes three main groups: AWL4, AWL5, and AWL6.


Over 270 samples were tested in the sample groups. Each webbing tested has a minimum of 5 samples and up to 8 samples. The larger sample sizes were done on webbings we experienced a lot of variance on. Most of the time this was attributed to short sample lengths.

Each webbing starts as a 5 foot sample and we tried to maximize this length by installing in the weblocks at the very end of the sample. Early on in the testing process, we weren't as diligent in this process, which accounted for a lot of the variance we saw in the testing.

For 25mm/1-inch webbings, we used the weblocks as intended. For 20mm webbings, we used spacers for the weblocks. All samples were installed in the weblocks in the standard, approved way.



Control Group Results

Control Group Results

AWL4 Results


AWL5 Results


AWL6 Results



Here we have the average results for each sample group:

  • AWL4 - 83.35% across all samples
  • AWL5 - 83.53% across all samples
  • AWL6 - 89.23% across both samples

Another interesting comparison is material type. Do specific materials perform better in specific weblocks? Let's see:


  • AWL4 - 87.76% across all samples
  • AWL5 - 87.43% across all samples
  • AWL6 - 92.41% across both samples


  • AWL4 - 85.84% across all samples
  • AWL5 - 85.14% across all samples
  • AWL6 - 93.79% across both samples

High Tech

  • AWL4 - 56.95% across all samples
  • AWL5 - 62.27% across all samples
  • AWL6 - 58.95% across both samples

The High Tech needs more data as we only had 2 different webbings to test. With our coming high tech webbings, we will be able to double that sample size, which will then be added to this test report.

Furthermore, another interesting comparison is width. Do 20mm webbings do better in a specific weblock? However 40% of our 20mm webbings are high tech, so that may be throwing the results off a bit:


  • AWL4 - 80.82% across all samples
  • AWL5 - 76.89% across all samples
  • AWL6 - 81.29% across both samples


  • AWL4 - 84.40% across all samples
  • AWL5 - 86.29% across all samples
  • AWL6 - 92.28% across both samples

Throughout the testing, one thing became very clear to be a major influence on the result: sample length. A lot of our early tests were done with long tails on the weblocks. For these webbings, we saw very large variance in the samples. If we were to do this study again, the tail lengths would be a standard for the experiment. I apologize about that inconsistency. For others that are interested in doing tests like this, we highly recommend maximizing your sample lengths as much as possible. Not only does that represent real-life usage more, it also allows room in the sample to equalize a lot better. Webbing flaws are exaggerated with short sample lengths.

Looking through the results on these tests, most webbings didn't really care if they were installed the wrong way in weblocks. There were a few exceptions though. Feather PRO did the worst of any low tech webbing. It slipped through all the weblocks instead of breaking. This was likely due to the extremely smooth weave that it has. Also, all the high tech webbings did not like being installed incorrectly in the weblocks. There are a number of factors that make high tech webbings more susceptible to slippage in this configuration, that we won't go into here.

Looking at the devices themselves, it's clear that the AWL6 did a lot better than the other two devices. This is mainly due to the bend at the end of the diverter (or start of the diverter when installed in the tested configurations). The AWL6 has a very large ended radius on the diverter coming off of the 38mm main diverter diameter. The AWL4 and 5 have very tight radii right at the end of the diverter, which is where most of these samples were breaking.


In general, weblocks function quite well even when the webbing is installed on the wrong side of the device. There are exceptions to this rule though, so it is best to avoid using weblocks in this orientation. It's nice to see and know that we are still able to retain at least 60% on just about any webbing no matter what the orientation is on the weblock though.

One last thing about this testing, we used the same 6 weblocks for the entire study. Each weblock was taken to over 20 kN, many times over 30 kN, at least 180 times. The AWL5 and AWL6, both being stronger than 80 kN and made from a single block of aluminum, did the best (we did end up going through about 6 front pins on the AWL5 though). These devices will continue to be used in our test machine. The AWL4's did quite a bit worse. The body is flaring out at the end, the anchor hole is splitting, and the hole for the front pin has elongated significantly. We don't have many more tests with these devices and may need to use a new set for future testing.

Used Devices

Thanks for reading through our tests results. If you have any questions or comments, please leave them below or get in contact with us.

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