Pull cords, also called rap lines and tag lines, have a variety of uses. They can be used to pull-up extra gear on aid climbs, extend the length of rappels by pairing them with lead ropes, and in an alpine context be used as ultralight fixed ropes or additional anchor material. Some can even be used for glacier travel and crevasse rescue. This video will look at their use for rappelling.

On climbs that have rappels that are longer than 35 meters it is generally necessary to carry two ropes (if you rappel with a single 70m rope folded in half, you can rappel a maximum of 35m). Pull-cords are often preferred over carrying a second climbing rope because they are much lighter weight and more compact. In fact, carrying a skinny single-rated rope and a thin pull cord is often lighter and more compact than carrying two half-ropes or twin ropes. Using a pull-cord an single-rated rope also greatly simplifies rope management at belays compared to systems that rely on two ropes in the belay system for lead climber fall protection (such as half or twin ropes).

Although there are many advantages, using pull cords requires a thorough understanding of how these cords can cause systems to fail due to differences in rope diameter and rope friction in a rappel device. This video shows a way to use a pull-cord coupled with a single-rated rope that greatly reduces the risk of system failure.