What is an 'etrier' used for in climbing?

An etrier, also known as a climbing ladder or aid ladder, is specifically designed to help climbers ascend vertical surfaces, particularly during aid climbing. They consist of a series of loops or steps that allow climbers to place their feet in them and pull themselves upwards, making it easier to ascend challenging sections of rock or ice where techniques like free climbing may not be feasible. The design of an etrier helps distribute the climber's weight and provides the necessary support without the need for extensive free climbing skills.

In contrast, options representing a tool for anchoring ropes, a device for descending, or a protective harness serve different purposes in climbing. While anchoring is crucial for safety, it does not relate directly to aiding vertical ascent like an etrier does. Similarly, devices for descending are focused on controlled descent rather than ascent. Lastly, a protective harness supports the climber but does not facilitate elevation in the same manner a set of loops in an etrier does. This contextual understanding clarifies the role and functionality of an etrier within climbing activities.