This tool is a simple yet effective device that assists a climber climbing up and down in SRT, or Single Rope Technique. The way the Rope Wrench Works is by using leverage to force the rope into an S shape and providing friction for a controlled descent. When engaged, the Rope Wrench acts much like a conventional descent device such as a Figure eight. When not engaged, the Rope Wrench provides no interference with ascending the rope. This allows the climber to work an entire tree using single rope technique.

The Rope Wrench is essentially a descent device that has a neutral gear that allows it to ascend the rope as well. Because of this neutral gear, it is imperative that the rope wrench not be used without a sturdy and trusted hitch.

The Rope Wrench is the “limb that goes with you”. It provides the same service to your climbing hitch that the Limb or cambium saver provides in dDRT.

About the Singing Tree Rope Wrench:

The ZK1 is designed as a friction assist tool. It is not meant as a rope clamp or as a fall arrest tool. It acts as a heat and friction sink, to allow the user’s friction hitch to adjust downwardly. IT IS NOT A CONNECTOR OR AN ASCENDER. Without the rope wrench, it is never advised to descend on a lone friction hitch. The Rope Wrench’s function is entirely dependent on the friction hitch that the climber chooses to implement. The friction hitch is what the climber will rely on for life support.

Choosing a friction Hitch:

Many different styles of friction hitch can be utilized. The important thing is that it must be rated for the application. Use a hitch cord that is supple and doesn’t loosen from the rope when ascending or not weighting the rope. A stiff or overly long hitch cord can work itself open and not engage immediately in case of a slip or a fall. It is recommended that the climber use hitch cord that can withstand some heat and not become compromised due to glazing. Visually and manually inspect your hitch cord frequently. The rules regarding hitch use in dDRT should be followed when using a hitch with the Rope Wrench. The hitch should be inspected before and during each use.

Length and style of Tether:

The length of the tether should be long enough to allow the wrench full motion and not interfere with the hitch itself. An overly long tether can be sloppy and twist around the rope. The climber must monitor and inspect the tether constantly during the course of a climb. Make sure that the tether does not snag on branches or become tangled in the
Rope Wrench itself. The tether can be made from any heavy duty cord and should be attached to the climbers hitch tending pulley and the Rope Wrench. A hitch tending pulley is not required for the rope wrench to work but it is highly recommended.

THE ROPE WRENCH IS NOT INTENEDED FOR LIFE SUPPORT PURPOSES and neither is the tether, however it is strongly recommended that you use the tether in adherence to normal life support guidelines as it is good practice.

Adjusting the Rope Wrench

The ZK-1 is adjustable depending on the rope that the user wishes to use. A thicker, arborist 16 strand will require the wrench to be open. In fully open mode, the friction will be less; therefore more weight will be placed on your hitch. This would be similar to climbing dDRT with a pulley. By tightening the wench, you can climb with smaller
diameter ropes and less friction is placed on the hitch. It is recommended that the climber adjust the Rope Wrench so the friction bushings are almost touching the rope but not so tight that it drags the wrench down during ascent. It is similar to adjusting a wheel bearing or a clutch. Tools needed are two 13mm or ½ inch wrenches and a pair of pliers
to hold the bushing while adjusting.

Rope Selection:

There are advantages to having a thick rope as it is easier to grip with your hands.
This allows the climber to swing through the canopy and footlock the rope easier.
The downside of a thicker rope is that it is heavier and does not accommodate many other rope tools such as foot and hand ascenders. A thinner rope can be faster when using other mechanical devices but can be harder to grip with your hands or footlock. Experiment with different ropes and levels of friction in the Rope Wrench.


While using the Rope Wrench during ascent, it is very important that slack always be kept out of the system. Regardless of the system being used dDRT or SRT, slack must always be avoided and exposes the climber to a dynamic fall. In order to do this, the hitch must not fall below your waist. The climber can pull the hitch up as he climbs using a variety of techniques. The sit stand method ensures that there is never any slack in the system. A chest harness or similar device that holds the system above your waist can be used in various rope walking configurations. The back of rope wrench
can sometimes be attached to a chest harness and it subsequently pulls the hitch up the rope behind it. MAKE SURE THAT THE HITCH DOES NOT LOOSEN DURING ASCENT to the point that it does not grip the rope if the climber slips or falls.


A well tied hitch will be very hard to disengage unless the wrench is partially engaged. It is important before descending to make sure that the wrench has begun to engage. DO NOT USE THE ROPE WRENCH TO ACTIVATE THE HITCH. Descent should be controlled and the hitch should operate in a manner very similar to the way it performs in dDDRT. To stop, let go and maintain position via the securely tied hitch.

Work Positioning:

In SRT, The rope is fixed at one end and does not move. Unlike the Tie In Point (TIP) in dDRT, the TIP in SRT can be anywhere secure such as the trunk of the tree, a solid limb high in the canopy, or a fixed remote object. The rope between the TIP and the climber must be visually inspected and kept from harm. All cutting implements should not
come near the life support system. It is also important to analyze the force generated on redirects from the climber to the TIP. The climber must understand the hazards involved in adopting any new climbing technique and practice “low and slow before attempting anything at height.

Midline attachable

The ZK-1 is designed to accommodate a Ball Lock Quick Release Pin in place of the Top Front bushing. This allows the Wrench to be attached mid line. To replace, remove all of the nuts from one side of the wrench and remove one side plate and the front bushing. Tighten the other two bushings in place leaving the front holes open. Use lock tight for
extra security when tightening the nuts. Adjust lower bushing to desired location and install Ball Lock Pin. With the Ball Lock Pin, the Rope Wrench is midline attachable. The Climber should never climb without the rope wrench on the line.