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Single, Half or Twin Ropes, What Does it All Mean?

A group of mountain guides practice short-rope techniques high in the alpine in Rocky Mountain National Park.

Single Rope

Let’s start with the simplest and probably the most common system, single rope. As the name suggests, you climb with a single rope clipping all your pieces of gear to the one rope. This is the system we normally use for sport climbing, trad climbing, and some alpine climbing. Its advantage is in its simplicity and is best suited to straighter routes but it does mean only short rappels (unless you carry a tagline).

My favorite rope for this type of climbing is the Sterling IonR 9.4mm XEROS Rope. This rope has the bi-pattern feature meaning the middle of the rope is easy to find as the pattern changes.

There are skinnier and also fatter single ropes, but the Ion offers great balance between weight and durability. As a guide, this is an important balance as I am often belaying two of these ropes at the same time. Get one too fat and I have to visit my physio with elbow problems. Too thin and I have to replace my rope often!

Half Rope

Rock climber rapells on double ropes down the Petit Grepon in Rocky Mountain National Park

Half ropes is a system you should get familiar with if you are a frequent ice climber, someone who enjoys wandering trad routes or likes sketchy rock. This system means you are always tied in and belayed on two ropes, but you only clip one strand of rope to each piece of protection. You can see this system in use, shown here on the Petit Grepon, one of 50 North American Classic rock climbs.

These ropes are pretty skinny from 9mm – 8mm and because of the width, they stretch a lot! This means they reduce the amount of force that is applied to pieces of protection, which can be a critical factor when you are talking about ice screws or other marginal protection.

Another bonus is the long rappel of having two ropes with you. A lot of half ropes these days are rated so that you can second on a single strand, but think hard about whether you want to be hanging from 8mm of rope with 1000ft of air below your feet.

My half rope of choice is the Sterling Duetto 8.4mm XEROS Rope. Although skinny and maybe not wearing so well if used a lot in the rock realm, I mostly use this rope for ice climbing when I want the minimum force going to my anchors. A nice thought with half ropes is this. I have 16.8mm of rope attached to me, which makes me feel pretty safe!

Twin Rope

Twin rope is the final and very euro rope technique (I am allowed to say this being from Europe). For this you tie into two ropes just like half ropes, but unlike half ropes you must clip both ropes to all the pieces of gear.

The advantage of this is you get to split the ropes between two people and get to carry a super skinny rope like Sterling’s Dyad 7.7mm XEROS Rope and you also get the advantage of a long rappel. You may see our guides doing this during one of our Chamonix Valley climbs, or perhaps on an ascent of the Matterhorn.

Visualization key for whether a rope is rated as single, twin or half
Left shows single rope, middle shows half rope and right shows twin ropes. Ropes are marked on their ends with symbols identifying the type.

So what is the best system?  Well, that depends.  Every climb presents different challenges and deciding which rope to climb on to give you the most safety, speed, versatility, and efficiency is up to the individual to decide. If you’re not sure how to tackle a specific objective, consider hiring a guide to help you plan and execute your climb. 


Ian Fowler
Certified Mountain Guide, Internationally-licensed Mountain Guide
Colorado Mountain School

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