If for some reason a climber has difficulty on rope [technical difficulty, injury from fallen rock, exhaustion, etc], it is imperative that someone QUICKLY get them off of the rope. Sitting motionless in a harness can cause "Harness Hang Syndrome". The climber eventually passes out, and as their body goes limp, it tips backward into a horizontal position with their abdomen (where the rope is attached to their harness) higher than their feet and head. When this occurs, the climber will NOT regain consciousness and will die within minutes unless rescued. So the students here are learning a "fixed brake" pick-off technique that allows them to assist a fellow climber to the bottom of the drop.