Ropes: Single, Half & Twin

Posted on Sep 22, 2014

It's been a while! I just realized that I haven't written in this space since June. The good news is that it's because we've had a busy summer.

This time I'm going to get a little more technical and less philisophical. Some questions I often hear are “What is the best rope system for climbing?” or “What is the difference between twin and half half ropes?” or “What should I buy as my first rope?”. I’ve answered these questions often enough that I think it may be of value to write something about this subject in this space.

In my view one rope system is not better than another. Each just has it’s own advantages and disadvantages. Each situation that you go into could make optimal use of a different rope system. In a perfect world a person would have a quiver of all the different rope systems and in different lengths and diameters, but that is of course is quite expensive.

Following is a list of the different systems, a few of their characteristics and their advantages and disadvantages:

Single Rope

Single ropes are designed to use for all applications in a single strand. The UIAAA symbol for a single rope is a circle with the number 1 in the middle of it. They range in diameter from traditional fat ropes of 11mm to some very modern singles as thin as 8.6mm!

The advantages of single ropes are that they are easy to manage in belaying and at belay stances and that they have the lightest weight per metre of all three rope options.

One disadvantage of single ropes is that on routes which wander a lot they require long extensions on protection and even then on very circuitous routes you could still end up with rope drag. Single ropes are not as good over edges as twin ropes but better than half ropes in this respect. Strength over edges is a particular concern with the very thin modern singles. Also single ropes give you only half the rappel length that you get with two rope systems.

Half Ropes

Half ropes are used in pairs but can be clipped individually to individual points of protection on lead. They are also rated for belaying a second on a single strand though caution is advised in this application in situations where the rope could be loaded over sharp edges. They are also rated for use in a single strand for glacier travel. The UIAA symbol for a half rope is a circle with a 1/2 fraction in the middle of it. Half ropes range in diameter from about 7.5mm to 9mm.

Half rope systems work well on routes that wander a lot without having to put lengthy extensions on placements. As mentioned above they can be used singly for glacier travel and to belay seconds on rock as long as sharp edges are not a concern. Half ropes also give full length rappel capability as you have two ropes.

Disadvantages of half ropes include that they are more difficult to manage in belaying and at stances, they have the heaviest weight per metre of all the rope systems and that they are not as good over edges as single or twin rope options.

Twin Ropes

Twin ropes are also used in pairs but can not be clipped individually. They are always clipped as a pair as if they were a single rope. They are not rated for use in a single strand though they can be a useful “backpacking” rope for short rappels or doubled for short leads. The UIAA symbol for twin ropes is two intersecting circles. Twin ropes come as thin as 7mm these days.

Because of the cumulative diameter of the two ropes twin ropes are the strongest rope system over sharp edges. Twin ropes of course offer full length rappel capability and they are a lighter weight rope system than half ropes but heavier than a single rope.

As both ropes must be clipped into all protection in a twin system, they are the same as single ropes on routes that wander a lot and will require long extensions on protection to avoid rope drag. As mentioned above one twin rope is does not meet the spec to use as a glacier rope or to belay a second on rock as you can with half ropes but it may have application as a lightweight “walkers rope”. As with half ropes, twins are more difficult to manage in belaying and at stances.

I hope that the above illustrates that there are good reasons to use each rope system in different circumstances. If you can not afford to own a lot of different ropes and are just starting out, it may be that the simplicity and lower cost of a single rope is the way to get going.

There are also questions of lengths, dry treatments, rope care etc. but I think I’ll leave those for another blog.

If you have questions please don’t hesitate to get in touch with me at

Happy autumn!

Jan and the team at Island Alpine Guides