CMI Anchor Sling for Climbing

The CMI anchor sling is a sewn webbing climbing sling for building anchors around stems, limbs and structures. Wrap it, clip both ends and you have a solid anchor for a climbing line, rigging point or rescue system.

What an anchor sling does

An anchor sling gives you a clean, strong attachment point where a branch union or a basal tie-in would be awkward or hard on the tree. You wrap the sling around a sound stem or limb, clip the ends with a locking carabiner, and attach your climbing line, a pulley or a rigging block.

Compared with tying your rope directly around a limb, a sling saves wear on the rope and makes the anchor easier to retrieve and inspect.

Slings also give you a clean way to choose exactly where your anchor sits. Instead of relying on a crotch that may pinch the rope, you can pick a sound section of stem and place the sling right where you want your tie-in.

Climbing sling uses on a tree job

Climbers use slings for a lot more than tie-ins. They make quick redirects, choke a limb for a positioning point, build a basal anchor for SRS, and give a rescuer a fast attachment point to a stem.

Many climbers carry one or two slings on the saddle at all times, alongside a pulley and a rope clamp like the Kong Duck, so they can build a simple rescue system without going back to the truck.

Practice building these setups on the ground first, so that rigging a sling at height is quick and the result is tidy and easy to check.

Choosing a length

Measure the stems you usually anchor to. A sling has to wrap the stem with enough length left over for the ends to meet at a narrow angle. Wide angles between the legs multiply the load on each leg and on the carabiner, so a longer sling is often the safer choice for big trunks.

Short slings are handy for small limbs and quick redirects; long ones for basal anchors and big spars.

When you are unsure, carry a longer sling. It can always be doubled or wrapped twice around a smaller stem, while a short sling cannot be made longer.

Inspection and care

Webbing is vulnerable to cuts, abrasion, heat and chemicals such as bar oil solvents and fuel. Check the whole length and the stitching before each use and retire the sling if you find cuts, fuzzing, stiffness, discoloration or damaged stitching. Keep it away from the saw and from sharp edges. Life-support gear has to meet the applicable standard and the manufacturer's instructions, get inspected before every climb, and be used only by trained climbers.

Store slings in a dry bag away from fuel and oil, and do not leave them in the sun for long periods, since UV exposure weakens webbing over time. Keep a note of when each sling went into service, and wash heavily soiled slings in cool water with mild soap, letting them air dry in the shade.