Singles, Halves and Twins

To start with, all of those who found today's blog by typing in the word "single" while looking for a dating site are going to be disappointed. And those of you who found this blog after typing in the word "twins" are going to be doubly disappointed...

Instead, this article will describe the different types of dynamic climbing ropes available to climbers and their uses. As the title indicates there are three types of ropes that are regularly used for rock, ice and alpine climbing. Following is a brief description of each type of rope and their uses:

Single Ropes: The single rope system is the most commonly used system in all of climbing. Most climbers will start with a single rope which is adequate for pretty much everything. As a result these are used on ice, rock and in mountaineering settings.

Single ropes are designed to be used alone. A leader doesn't need a second rope to ensure security. When leading, he will only clip the single strand that he is tied to into the protection.


Single rope diameters range from 9.2 mm to 11 mms and vary in length. Most climbers currently use 60-meter ropes. The greater the diameter of the rope, the more wear and tear the rope can handle. However, though alpine ropes tend to wear out the fastest, it's probably not a good idea to get the heaviest rope that you can find for glacier travel.

Most climbers will try to buy a light single rope that can be used in a variety of functions. Heavy 11 mm ropes really only exist for two reasons, search and rescue teams and big wall climbers. Most people  purchase ropes that range from 9.5-10.3.

Single ropes will have this insignia on the end.

Single ropes are the least expensive alternative. Each of the other systems described here require two ropes to be functional.

Half Ropes:

Half ropes -- often called Double Ropes -- have a smaller diameter (8-9 mm) and are designed to be used in pairs. As a climber leads, he is supposed to clip each rope independently, swapping ropes as he passes each piece of protection.

Half ropes will have this insignia on the end of the rope.

The concept behind half ropes is excellent. They provide a number of advantages. First, if the route wanders up the crag, clipping the opposite rope each time you move up will reduce drag. Second, you will always have two ropes for double rope rappels. Third, you can share the weight of the ropes on the  approach with your partner. Fourth, in the event of an emergency you have double the length to get down quickly. And fifth, in the event of a bad leader fall if one rope is severed, the other rope will still catch the falling climber.
While the concept is excellent, in practice half ropes can be difficult to manage. It will take most climbers a fair bit of time to completely wire all the idiosyncrasies of working with two ropes simultaneously.

Some climbers do elect to use half-ropes for glacier travel. However, one should be very careful when doing this. Stepping on a half-rope with crampons will do a lot more damage than in a single rope. It should go without saying that ropes that see damage from crampons, regardless of diameter, should be retired.

Twin Ropes:

The twin rope system employs two small diameter ropes (usually 7-8 mm) together as if they are one rope. In other words, both ropes go through every piece of protection.

Twin ropes will have this insignia on the end of the rope.

The advantages to the twin rope system are quite similar to the advantages of the single rope system. The exception is that because of the fact that the twin ropes are being used the same way as a single rope, the same type of drag you encounter with single ropes will be apparent.

It is not possible to use twin ropes like half ropes, clipping one rope to one piece and the other rope to the next. The stretch in twin ropes is significantly greater than in half ropes and using them like this could lead to a significant leader fall.

Another problem that some climbers encounter with twin ropes revolves around belay devices. Not all autoblocking belay devices will work with twin ropes. If you elect to use this system, make sure that the ropes will not slip while belaying.

The question has come up in the past as to whether a twin rope should be used on a glacier. The answer is no. There is too much stretch in these ropes for this application and the likelihood of hitting something at the bottom of the crevasse or getting "corked" is too high.

It's good for climbers to be aware of a number of different rope systems. Ideally, you become familiar enough and experienced enough with each of these that you will be able to use the system that works the best for each and every climb that you plan.

--Jason D. Martin