Tree Climbing Multicenders: Akimbo, Unicender (Uni), Rope Wrench (RW), Hitch Hiker (HH2), Rope Runner (RR) & the BullDog Bone (BDB)

Over at the TreeBuzz forum, I asked what seasoned and experienced tree climbers were using, in terms of the latest and greatest mechanical SRT multicending tree climbing devices. SRT (single rope technique or static, fixed or stationary line climbing) has transformed recreational 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.

The Rope Wrench and the Hitch Hiker both use hand-tied friction-cords, aka: prusik cords, tied into rope-grabbing hitch knots which connect directly to these devices. 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.  Once the friction hitch is properly tied, dressed and set, these devices are almost as effective as their fully-mechanical competitors, except for some sit-back that occurs each time these hitch knots are weighted.

Friction hitch/knots, although they can become tightly bound, are more gentle on ropes and better for dissipating heat, compared to the teeth on mechanical ascenders that not only absorb heat, but can potentially strip the cover off a rope when shock loaded. Friction cords are also far less expensive, compared to the cost to replace or retool a worn out mechanical multicending device.

The Unicender, Rope Runner, BullDog Bone and the Akimbo  are completely mechanical multicending devices. They eliminate the use of friction cords altogether. These devices eliminate the sit-back, common among hitch-knot users. The efficiency can vary, depending on climber’s size, rope width, type and make of climbing line and even weather conditions, but they all seem to perform well with static 11mm/7/16″ climbing lines.

As a beginning SRT rec-climber, I began climbing with a Rope Wrench, using a dependable 5-wrap Michocan (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 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 Hitch Hiker is possibly the best multicending device ever. It’s noted for its overall simplicity and for being compact and efficient when used at different climbing angles. Unlike the Rope Wrench, it uses an unspliced friction cord that’s threaded through a dog-bone like metal bar, secured with fisherman’s  stopper knots on both sides. A steel carabiner or Tree Quickie also adds friction to the Hitch Hiker’s climbing line when weighted. Installing the Hitch Hiker is a bit more tedious than other devices, but once the friction knot is properly dialed in, it’s a top performer and the most 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. They both require some getting used to, in terms of getting the prusic knot properly tied, dressed and set. Although the Hitch Hiker may have a slightly steeper learning-curve in terms of finding the right balance between the hitch knot and the climbing line, this is a favorite multicending device among many experienced and seasoned climbers.

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 it’s being integrated into one of these two devices. In this regard, the hitch knots tend to bind and become increasingly more difficult to loosen, when necessary.

While many commercial grade friction cords are heat rated for climbing, excessive friction may cause scorching on the cord itself. By rubbing it back and forth against tree bark, it is possible to scrape off the excess scorched material, but friction cords will wear out over time.

The Unicender is a compact, fully self-contained and mid-line attachable ascending and descending device. It works well on both SRT and DRT 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 Uni 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.

The risk of an object or falling limb striking the Uni’s upper arm, or any multicending device, may cause an unintentional or accidental release from the climbing line. This may occur as a result of falling debris or improper use and while it may only have a temporary effect while the pressure is being exerted, then the device should re-engage. However, the end result may potentially cause an unintended fall and/or a shock-load to you and your climbing system.

Based on the high friction demand placed on the Unicender, due to factors that may include an unwashed climbing line and due to abrasion, over time it will wear out and eventually begin to slip on the rope.  For about $200, versus the $300+ replacement cost, you can get the device restored and refurbished through Rock Exotica, but many production-climbers prefer the Rope Runner whose components can be replaced, with easily available parts.

For someone like myself who climbs strictly for recreation, or much less than someone like a production climbing tree care professional, the Unicender is a top contender because of it’s overall user-friendliness, compactness and for being fully self-contained.

Each of these devices have their pros and cons and there great things to say about all these devices, once you get everything nicely dialed in. What I’m curious to know is how well all these devices perform, side by side, with regard to heat retention and friction, namely on descents that are 200′ or longer.  Changing over to a Petzl Rig or other similar mechanical breaking devices may be preferred for longer descents, so keep in mind, these devices are all subject to the laws of physics.

Friction and heat build-up can scorch and even melt a climbing line, especially if a climber isn’t being attentive enough to their gear when descending on any repelling device. 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 has designed a Uni accessory to mitigate friction, known as the Drum and it looks like it makes things a lot better for Uni users because of the way it helps improve both friction-management, reduces wear and tear and provides for an easy lock off.  Richard demonstrates its installation and use in the following video.

How the Drum may effect the Uni, 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 makers of the Uni, with respect to them possibly sanctioning the Drum, or any such modifications to their original design.

Another addition to the multicender family is the Rope Runner. As demonstrated below, it uses a mechanical hitch, very similar to the Rope Wrench, but without any friction cord. It has two auto-locking removable slick pins and a steel carabiner to guide the rope through the device, but is otherwise fully self-contained.

Singing Tree, makers of the Rope Runner sold the RR’s rights to TreeStuff, who were then bought out by SherrillTree. According to Kevin Bingham, the inventor of the RR, the RW and founder of Singing Tree, the original Rope Runner can be easily maintained in top working condition with economical and easily available interchangeable replacement parts, whereas the Rope Runner 2 is designed with no detachable parts. The Rope Runner 2 would eliminate the long term manageability of the original Rope Runner, so it’s uncertain if there will ever be a Rope Runner 2.

Another prototype product was available through unconventional means and involved a buy-and-use-at-your-own-risk disclaimer. The BullDog Bone is similar to the Akimbo’s fundamental design. This is a highly regarded multicending device, favored among many production climbers may still be available through an individual member belonging to the TreeBuzz group.

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.

Here’s a preview video of the Akimbo. There’s already quite a stir in the tree climbing community about this innovative product. It is both SRT and DRT friendly,  aesthetically pleasing, compact, adjustable for use on different width ropes, using no external locking pins and it doesn’t rely on using a friction cord.  It uses two adjustable bollards, to assure better conformity with different size climbing lines. Unfortunately it’s still in the initial R&D/production phase and not expected to hit the shelves until maybe sometime in 2018.

As a newbie I think I made a good choice by starting with the Rope Wrench and then upgrading to the Unicender, once I became better trained and understood the fundamentals of climbing. I prefer the simplicity of the Uni, the efficiency and ease of installation, over that of more temperamental hitch cords, or the Rope Runner. I also now use a Hitch Hiker, both for secondary climbing systems, and as a backup for the Uni.

Over time, I’ve come to appreciate and deeply respect the overall benefits a friction cord has, 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 I can totally rely on several dependable multicending SRT devices.

In conclusion and based on the group’s feedback, I recommend the Rope Wrench, Hitch Hiker or the Rope Runner for daily production work, otherwise for rec climbing purposes, the Unicender or Rope Wrench, may be a more user-friendly choice for beginners, depending on where and how often you plan to climb.  Seasoned and old-school climbers may prefer the Hitch Hiker, based on both cost and the indestructible nature of its design.

Of course, everything may all change when the Akimbo becomes available, so please stayed tuned.  has published a description, a video and photos. They say Rock Exotica’s Akimbo will be out later this spring.