Tree Climbing Multicenders: Rope Runner Pro (RRP), Akimbo, Unicender (Uni), Rope Wrench (RW), Hitch Hiker (HH2 & HHX), Rope Runner (RR), ZigZag/Chicane (ZZ) & the BullDog Bone (BDB)

Technical tree climbers have a growing number of mechanical SRT multicending tree climbing devices to choose from. SRT (single rope technique or static, fixed or stationary line climbing) has transformed tree climbing, enabling climbers to ascend into and maneuver within the canopies, using the least amount of wasted energy.

In the last twenty years new climbing products and innovations like professional grade multicenders, or devices that combine ascending and descending functions into one device, within the SRT framework have become available. Choosing which device is best suited to beginners or advanced users depends on a number of personal preferences.

In case you didn’t already know, the main difference between stationary-rope-technique (SRT) and doubled-rope-technique (DdRT) is that with DdRT, you pull two times, or double the length of a moving rope, going up and around a limb and back down. The climber, controls both ends of the moving rope and has a 2:1 mechanical advantage. That makes it easier to lift oneself up a climbing line, but it only advances the climber half as far, when compared to SRT’s 1:1 advantage.

Ascending SRT on a stationary climbing line when using a multicender, together with a foot and a knee ascender, creates a true Rope-Walking climbing system. This allows the climber’s weight to be distributed onto both the foot and knee ascenders, using both legs in an alternating way, while leaving the arms free to use more for guiding, positioning and stability, thereby conserving upper body strength, as well. These devices when combined, create an ergonomic, efficient an extremely popular SRT climbing system. Various brands of ascenders and multicenders, provide countless ways to build a true Rope-Walking climbing system.

Homemade or commercially available gas or electric powered ascenders, including the Raptor and the Ronin, may offer an easier climbing solution using mechanical automation, rather than climbing unassisted and under one’s own power. Using a counter-balanced weight also enables climbers to mitigate or eliminate the weight of their load, but when it comes to climbing solely under one’s own power, the Ropewalking system is my favorite climbing style for ascending a stationary rope.

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The Rope Wrench and the Hitch Hiker both use hand-tied friction-cords, aka: prusik cords, tied into rope-grabbing hitch knots. The effectiveness of either device can vary, based on the quality and type of friction hitch, the type of friction cord, as well as, its direct relationship with the climbing line and the climber.  The friction cord’s diameter must be less than the rope’s diameter, in order to properly perform. Once the friction hitch is properly tied, dressed and set, these devices are as effective as the mechanical multicenders, except for more sit-back that occurs each time the hitch knots are weighted. Most hitches also have a tendency to bind and can generally become more difficult to manage, when weighted and under tension.

Friction hitches or rope grabbing knots, although they can become tightly bound, are gentle on ropes and well suited for dissipating heat, compared to the metallic friction points, or way more abrasive teeth on certain types of hand, feet, knee or chest ascenders. These teeth, when shock loaded, can strip the cover off a rope. Friction cords are also economical and easy to replace, compared to the cost to replace or retool a worn out mechanical multicending device.

A major concern among hitch cord users is, or should be, knowing when to retire a used cord. While many commercial grade friction cords are heat rated for climbing, excessive friction may cause scorching on the cord itself. By rubbing the cord back and forth against tree bark, it may be possible to scrape off scorched and sappy material.

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The Rope Runner Pro, Rope Runner, Akimbo, Unicender, ZigZag/Chicane combo and the Bulldog Bone are completely mechanical multicending devices. They eliminate the use of friction cords altogether. These devices reduce sit-back, compared to other hitch cord based multicenders. Overall efficiency of each device depends on the rope type, a climber’s weight, the weather and other known and unknown factors. These devices are all intended for use on manufacturer recommended static climbing ropes somewhere in the 11mm to 13mm diameter range.

I began climbing with a Rope Wrench, using a dependable 5-wrap Michoacan (aka: Martin) friction hitch/knot on a 28″ sewn eye-and-eye Bee-Line prusik cord and a Hitch-Climber pulley. While this device is dependable, keeping a close eye on the friction knot and adjusting it periodically to be sure it grabs and releases the rope when needed is always mission critical. Based on my weight, I tried a number of different prusik cords and hitch knots, until finding ones that were better suited to grabbing and releasing my weighted climbing line.

The Rope Wrench itself is incomplete without a recommended eye & eye hitch cord, a hitch tending pulley, 12″ stiff tether and a locking carabiner. The Rope Wrench itself is positioned on one end of tether, above the hitch knot, creating a bend in the climbing line. A hand spliced or sewn spliced eye & Eye prusik cord connects the to the pulley and carabiner, creating an effect that is similar to a DdRT climbing system, but with the benefits of an SRT system. The Rope Wrench’s effect places a bend in the rope, which reduces tension on the hitch knot, similar to DdRT, making it less likely to bind. A tending device, connects the tether to the climber’s chest harness, neck loop, or an over the shoulder lanyard.

The Rope Wrench has the distinction of being the only multicender for just SRT climbing. Although, switching from SRT to DdRT is as simple as reaching the canopy tie-in-point, lanyarding in for safety, and changing the tie in point from a stationary to a moving rope system. At that point, disengaging the Rope Wrench from the climbing line, while leaving the hitch tending pulley in place will then complete the change-over. Care should be given to not drop the slic pin when up in the tree and by being safely tied in with a secured climbing lanyard. Fortunately the slic pin has two points of engagement. Leaving the pin partially engaged, with enough room to take the Rope Wrench on or off the rope is possible.

The Chicane/ZigZag combination is the most expensive and currently one of the most popular multicenders among production climbers. While it’s based on the exact same principle used by the Rope Wrench, the mechanical rope grab works like a hitch knot and avoids the sort of binding issues associated with hitch knots. This offers climbers a reliable, solid, well conceived mechanical alternative, providing the strength and consistency needed for both SRT and DdRT climbing systems. Designed for use on static climbing ropes between 11.5mm and 13 mm in diameter , the 2019 ZigZag Plus comes with a built-in swivel, or the slightly less expensive 2019 ZigZag which has no built-in swivel.

Unlike other multicenders, the ZigZag is not mid-line attachable and that’s a big drawback for some, especially when advancing and or alternating between climbing lines. As noted below, the ZigZag can be used with a Rope Wrench in place of the Chicane in an SRT system, but the upgraded ZigZag is now stronger and more robust than its predecessors and the Chicane has a modified tether with a hand-grip, similar to a hand ascender.

The RopeTek Hitch Hiker 2 is a personal favorite and possibly the best multicending device ever made. It’s noted for its overall strength, simplicity and for being compact and efficient when used at different climbing angles. Unlike the Rope Wrench which uses an eye & eye cord, the Hitch Hiker 2 uses a friction cord that’s threaded through a dog-bone like metal bar, secured with a fisherman’s knot or other suitable stopper knots on both sides. A steel carabiner and the dog bone add friction to the Hitch Hiker 2’s climbing line when weighted, enabling the prusik knot to perform smoothly and reliably.

A Hitch Hiker 2 needs to be augmented for tending. I believe the best tending option is the plastic holster, but a short 5″ rope with two sewn eyes, metal wire or a loop of throw line are options as well. Tending the Hitch Hiker by attaching it onto a climber’s chest harness, neck loop or an over-the-shoulder-lanyard enables the device to self-tend.

Installing the hitch cord on any Hitch Hiker is a bit more tedious than other devices, but wrapping the friction cord around the climbing line and tying stopper knots on the ends of the friction cord is simple to learn. Once the friction hitch is dialed in with minimal sit-back, the hitch performs exceptionally well. It’s a very efficient, compact, rugged, manageable, reliable and economical multicender.

Both the Hitch Hiker and the Rope Wrench are mid-line attachable. Because prusik cords are economical, easily available and rope-friendly, both of these devices are very popular multicending contenders for hitch knot users. They can take some getting used to, in terms of getting your preferred cord and hitch knot properly tied, dressed and set. Of the two, the Hitch Hiker is the least expensive to own and it’s built like a tank.

As shown in the above video, Climbing Innovations offers a variation of the Rope Tek Hitch Hiker 2, using a Tree Quickie, in place of the original CT steel carabiner used by Rope Tek. The redesigned Hitch Hiker X no longer has riveted bumps on it’s sides, leaving smooth surfaces on both sides for the Tree Quickie to move more freely when tending. On the Hitch Hiker 2 when the plastic tending holster, it keeps the Tree Quickie from hitting the side rivets, but that’s only if you’re thinking about replacing the steel carabiner with the compact Tree Quickie. Alternatively, I prefer to connect my rope bridge swivel directly to the Hitch Hiker 2’s steel carabiner, keeping the hardware footprint to a minimum.

When friction knots are properly tied, dressed and set using either the Rope Wrench or Hitch Hiker, they perform adequately with minimal sit-back. A friction cord under load and heavy use will eventually wear out, causing it to lose integrity, mainly due to heat build-up and friction.  Friction hitch/knots are not recommend solely for use as a primary repelling device on SRT, unless its being integrated into one of these two devices.

The Unicender is a compact, fully self-contained and mid-line attachable ascending and descending device. It works well on both SRT and DdRT climbing systems. There’s a slight transitional bump or jerkiness that happens when transitioning to and from ascent to decent, but getting used to that is easy. Wrapping the rope around the Unicender on descent is strongly advised, rather than pinching the two outside arms together with your hand and holding on for dear life. The later option is dangerous under any condition and should be avoided.

Based on the high friction demand placed on the Unicender, especially due to factors that may include an unwashed climbing line causing abrasion, and through normal wear and tear will eventually take it’s toll. Equipment of this caliber is usually dependable for maybe three years, depending on each individual’s climbing characteristics.

I’ve climbed on my Unicender many times with no slippage, but I am seeing some signs of friction wear on the anodized finish. Although the Unicender has no replaceable parts, there are two options to address signs of excessive wear. For about $200, versus the $300+ replacement cost, you can get the device restored and refurbished through Rock Exotica. In comparison, the Rope Runner has wearable bollards and other components which can easily be replaced with available replacement parts. This may be the one of the most notable differences between the various mechanical multicenders.

For someone like myself who climbs strictly for recreation, home gardening or much less than someone like a tree care professional who regularly hauls cutting and rigging equipment into the trees, from a beginner’s standpoint, the Unicender remains a top contender because of its smooth tending capacity, overall user-friendliness, being mid-line attachable, compactness and especially for being fully self-contained, with no removable pins or parts. The only drawback, as a matter of preference and depending on wear and rope type, may be the use of the Unicender’s descending function, which may run a bit fast and loose for some.

The risk of an object or falling limb striking the Unicender’s or Akimbo’s upper arm, or any multicending device for that mater, may cause an unintentional or accidental release from the climbing line. Some multicender manufacturers warn against using hand ascenders with foot-loops, but when I am on a ropewalking system with a foot and knee ascender, on longer ascents I’ll usually include a hand ascender above my multicender, but without attaching a foot-loop onto it. This makes it easier to grip and pull myself up the rope.

I wonder how well all these devices perform in side by side comparisons, with regard to heat retention and dissipation, namely on rapid descents that are 200′ or longer. Changing over to a descender from a  multicending system is not required, but a climber may opt to use a Petzl Rig, or another similar type of descending device , such as those with anti-panic features that are well designed more specifically for longer, heavier, and/or more controllable descents. Always keep in mind, these devices are all subject to the same laws of physics, relative to friction and heat retention.

Friction and heat build-up can scorch and actually start to melt a polyester covered climbing line, especially if a climber is ripping around and not being attentive enough to their gear. A scuba-diver is subject to embolisms when ascending too quickly, whereas a descending climber depending on a friction knot and or mechanical device may overheat and melt a polyester climbing line when rappelling too quickly for a long duration.

Richard Mumford at ClimbingInnovations.com has designed a Unicender accessory to mitigate friction, known as the Drum and it looks like it may make things a bit better for Unicender users because of the way it helps improve friction-management and provides for an easy lock off.  Richard demonstrates its installation and use in the following video.

How the Drum may effect the overall performance of the Unicender, for better or worse, is uncertain, but it does alter the original design in an attempt to make it more durable and functional. I’m not aware of any formal response from the inventor Morgan Thompson, or Rock Exotica who manufacturers the Unicender, with respect to them possibly sanctioning the Drum, or any such modifications to the original design.

Thompson Tree Tools, together with Rock Exotica now appears to be preparing for the release of a new Unicender 2, along with their new foot/knee ascenders, as shown here on this Instagram video.

The Rope Runner, as demonstrated below, uses a mechanical hitch, very similar to the Rope Wrench, but without any friction cord. It has two auto-locking removable slic pins and uses a carabiner to guide the rope through the device and secure it onto a climbing harness. With proper care, by replacing warn out slic pins, one-use nuts, and the spring from becoming overly worn, a climber can maintain a Rope Runner almost indefinitely.

The Rope Runner performs well on a wide variety of static climbing ropes between 11mm and 13mm. It’s a top choice for a mechanical multicending device, especially for production climbers. This device also requires the use of a tending device like a chest harness, or an over-the-shoulder lanyard. The device’s built-in pulley enables very smooth tending, especially when using a RAD system or when limb walking. The Rope Runner can be augmented with a 4SRT Birdflap, to give the device’s bird a bigger area for the climber to grip onto when descending.

The Rope Runner is comprised of machined components including the body, the bird assembly, the tether assembly, the tender-pulley assembly, the lever assembly with the axle spring, two slic pins and the retaining washers. Installation is relatively simple with rope guides etched directly onto the device. The rope is secured between the bird assembly with a slic pin, in the level assembly using a slic pin. The upper friction bollard is adjustable, using the one-use bolt. A carabiner secures the tending pulley assembly and connects onto the climber’s saddle.

On a personal note, I know a successful competitive tree climber who prefers using the Rope Runner with a worn down upper friction bollard. Even though a replacement bollard is available, he is hesitant to replace it, especially after winning a speed climbing competition. He says it gives him added efficiency and control, but the manufacturer may suggest otherwise. While the design may seem rather simplistic, unrefined and clunky, the Rope Runner is affordable, efficient and serviceable.

Singing Tree, makers of the Rope Runner sold the RR’s rights to TreeStuff, who were then bought out by SherrillTree. According to the Singing Tree founder, Kevin Bingham, the original Rope Runner is well suited for commercial use because of its component based design that vastly extends its longevity when properly maintained.

While newer designs do exist, the market eagerly awaits an updated Rope Runner, perhaps with a better tending system, more user-friendly bird design and other overall refinements. If a Rope Runner 2 is more expensive and less serviceable than the original, it may not be able to compete with itself. However, on May 23, 2020, Kevin Bingham, showcased the new Rope Runner Pro, produced by Notch, as seen in the following Youtube video where Kevin showcases the device and his exceptional climbing skills. Treestuff concurrently announced an exclusive arrangement to initially sell these in the summer of 2020.

At first glance, the Rope Runner Pro looks like a well thought out upgrade, while maintaining the same high level of serviceability and affordable price, when compared to the original Rope Runner. The initial selling price is just under $350.00, offering a lot of bang for the buck. The most notable improvement is a non-drop-able design that enables the device to remain connected to the rope bridge at all times, while being installed and removed from a climbing line. The Rope Runner Pro no longer breaks apart into three pieces, like its predecessor. While there are many subtle and not so subtle refinements, the end result far exceeded my original expectations and is a testament to brilliance, attention to detail, innovation and hard work on the part of the designers and developers.

The Singing Tree emblem is stamped into Rope Runner Pro’s forged metal and adds a nice touch, paying homage and respect to Kevin Bingham and his company that first produced the original Rope Runner and the Rope Wrench. There is additional information embossed into the device, including a for use by 1x climber guideline, a max weight guideline of 140kg, or 308.6 lbs, and a rope size guideline in the 11mm to 13mm range. Personally, I can hardly wait to get my hands on one of these.

The BullDog Bone is not sold commercially through the usual retail outlets and it comes with a buy-and-use-at-your-own-risk disclaimer. It may be available through a private party who makes and sells these. By doing a search on the TreeBuzz forum using the keywords, “BullDog Bone“, it should provide access to the individual who sells these. The BullDog Bone is in itself a forerunner to the Akimbo which is collaboratively based on its initial design concept.

Like the Unicender and Rope Runner, the BullDog Bone is a fully mechanical, self contained multicending device that has the appearance of being a top contending option, but the BullDog Bone isn’t a mass marketed product and for that reason, it falls outside of my personal comfort level when it comes to testing and researching new products of this magnitude. If it were to become available on a retail level, my ability to compare this to other similar products would be less biased.

The Akimbo became available, as of January 25, 2019. It is both SRT and DdRT friendly,  aesthetically pleasing, compact, adjustable for use on static climbing ropes on specific “approved” ropes between 11.5mm and 13mm diameters. It uses no external locking pins and it doesn’t rely on a friction cord.  It uses two adjustable bollards, to assure better conformity with different size climbing lines. The tending system is unique and includes a wire gated hook. This may take a bit of time for climbers to get adjusted to and hopefully come to appreciate.

In the following video, the Akimbo’s creator, Jaime Merritt, shows a couple tending methods, using a climbing lanyard. The Petzl Torse Croll Harness, or any number of other chest harness options can serve the same tending function. The Akimbo’s wire-gated break-away tending system gets mixed reviews and for that reason, using a loop of throw line girth hitched around the Akimbo’s carabiner can effectively and safely alleviate the Akimbo’s tending clip’s break away aspect.

Setting the proper bollard settings is required every time a climber uses their Akimbo and different climbers may have different settings on the same or similar ropes. Some climbers report that the settings differ, even on the same rope, depending on whether the rope is wet or dry. Using ropes under 11.5mm on the Akimbo may cause slippage and Rock Exotica has published their list of approved weight rated ropes, some with a 220lb weight limit, and some with a 286lb weight limit. Following these guidelines is highly recommended.

The Akimbo’s approved rope list appears on Rock Exotica’s web site and is expected to grow over time as more ropes get tested and new ropes become available. My personal experience when trying several non-approved ropes has been less than favorable when it came down to not being able to dial into functionally safe and usable bollard adjustments. For that reason, I bought a new 150′ hank of Drenaline by Teufelberger, which runs great for me. I now enjoy the Akimbo on an approved rope and feel more secure and confident doing so.

Perhaps the Akimbo will someday evolve and include self-adjusting bollards that work on a broader variety of rope sizes, or maybe adapt to using a non-breakaway tending point. Despite the set up time, hard to see bollard pin settings and the unique learning curve, the efficiency and compactness of the Akimbo, when used properly, puts it in a class of its own.

I initially began climbing with the Rope Wrench and then the Unicender, once I became better trained and understood the fundamentals of climbing. The Uni has no sit-back and tends so much better than the Rope Wrench‘s friction hitch, its like day and night. I then acquired a Hitch Hiker 2, which I enjoy for the sake of its compactness and rope-friendly efficiency. Eventually, I then acquired the Akimbo, and was one of the first to receive shipment, having been one of the first to place a pre-order. At that point, the temptation to buy a steeply discounted Rope Runner became too unbearable, so I bought a Rope Runner to add to my collection.

I’ve gone full circle. I’ve come to appreciate and deeply respect the overall benefits of rope-friendly friction cords, in comparison to less rope-friendly mechanical ascending products that flatten and/or use teeth like cams to grip the climbing line. I’m also comforted knowing how we all can totally rely on each of these multicending SRT devices, when used responsibly and safely, in accordance with the manufacturer’s guidelines.

Given the diversity of static climbing ropes, it’s becoming apparent that certain ropes perform better than others, depending on the specific multicending device. The Akimbo is geared toward ropes in the 11.5mm-13mm range, while other multicenders also work on smaller diameter ropes. Of all the available static climbing ropes, some devices may or may not work properly, so be sure you are buying a rope that is properly suited to your climbing system/s.

In conclusion and based on feedback from others, I recommend the ZigZag/Chicane combination as a top pick for production climbers who mostly climb on a moving rope system. The non-mid-line attachable issue can be a deal breaker for some climbers, while others integrate this into their climbing style with relative ease. The Hitch Hiker or the Rope Runner are also beautifully suited for daily production work. The new Rope Runner Pro is very promising and when it becomes available this summer, there will be lots more feedback, I’m sure.

The Unicender is the most user friendly and easiest to install and remove from a climbing rope. The Unicender is also my top choice for use as a lanyard adjusting rope-grab and secondary climbing system. Its easily installed and removed, mid-line, while performing well in both a stationary and moving rope system.

Beginners usually learn to climb on a Rope Wrench, due to the fact that they are more visually and physically verifiable by an instructor, crew boss, or climbing facilitator. The Rope Wrench is also a top choice for climbing competitions where climbers are provided an equal and level playing field, while mitigating risks to the facilitators who may not have time to inspect individual climbing systems for each competitor.

While the Akimbo and the Unicender have no removable parts, wear and tear around the rope’s contact points is a factor, depending on the amount and degree of use. For that matter, keeping your ropes clean will help extend the life of all mechanical multicending devices.

The Akimbo is favored among many, due to it having the smallest and most compact footprint. Its ability to operate smoothly, subject to specific ropes, settings and other variables is another concern. It too has a tendency to wear out around the friction points, but the breaking in of the device is also a noted benefit. The Akimbo is pending CE certification and even though it satisfies a number of important usability issues, the finicky bollard settings and recommended limited use, except on manufacturer approved ropes has lessened its overall appeal.

The ZigZag/Chicane combination is a solid alternative to using hitch tending pulley with a Rope Wrench. Some climbers have successfully integrated a ZigZag with the Rope Wrench, thereby replacing the Wrench’s hitch cord with the ZigZag. This ZigZag/Rope Wrench combination is another SRT multicending option to consider, as well.

Seasoned and old-school climbers may prefer the Hitch Hiker or Rope Wrench, when tree sap might otherwise interfere with the function of any mechanical multicender. Wet weather may also impact a decision to use a hitch cord or mechanical multicending device. The Rope Runner, Rope Wrench and the Hitch Hiker have replaceable components which also make them good for all-around tree climbers.

Depending on your preferred climbing style/s, the Rope Runner may not be as practical for moving rope systems as a Rope Wrench or a ZigZag/Chicane, but its ideal for static rope systems. At present, my top two choices for mechanical and non-mechanical multicenders are the Rope Runner and the Hitch Hiker.

This article is updated periodically, as needed to hopefully keep up with new products and industry standards. Social media apps, along with the individual contributors at the TreeBuzz Forum, are among my most valued resources for timely information, varied opinions and shared experiences from all branches of the tree climbing community.

Please leave a comment. Your feedback is appreciated.

Related Information: My Gear Bag, Where to Buy Tree Climbing Gear & Tree Climbing Gear for the Fully Autonomous Recreational Tree Climber