This slower absorption reduces the impact of the fall and the likelihood of a catastrophic outcome. Rock climbing ropes are generally categorized into three main types: single, twin and half or double.
Single ropes are generally between 9.5 mm and 11 mm in width, while they vary greatly in length. The standard for single ropes, though, holds around 10.5 mm by 50 mm. Designed to be used alone, single ropes are the most common type of climbing rope. They are used for top-roping, sport climbing and trad climbing. Twin ropes are made of two separate ropes of the same size, meant to be clipped together through each piece of gear and used as one rope. Twin ropes are extremely thin, usually about 7.6 mm each. They are mostly used in ultra-long rock, ice, mixed routes and expeditions that require lightweight equipment.
Half or double ropes are similar to twin ropes in that they are also two ropes of the same size and used as a pair, but the similarity ends there. Unlike twin ropes, with half ropes, only one rope is clipped through each piece of gear. The climber alternates which rope is clipped through each piece. Considerably thicker than twin ropes, this type of climbing rope is about 8.8 mm thick, and can hold a climber in a fall if the other rope fails. Its alternating clips also reduce rope drag. Half ropes are good for long, wandering climbs and trails with treacherous traverses or sharp rocks.
When considering climbing ropes, a potential buyer should ask him or herself what he or she wants and needs in the way of: rope diameter, rope weight, weight the rope will be supporting, terrain, weather, rope construction, middle marks and bi-patterns and dry treatments. A middle mark is placed on a rope with black paint or thread to identify the middle of the rope. Bi-patterns or bi-colors are a change in weave pattern that help a climber clearly differentiate between the two ropes, as well as easily identify the midpoint. These tools contribute to the safety of a climber.