Final answer:
A 180 degree elevation in hair cutting is used to lift the hair straight up from the head to create layers that are shorter on top and longer at the bottom, resulting in a haircut with more volume and movement.
Step-by-step explanation:
In hair cutting, a 180 degree elevation refers to the angle at which the hair is held or lifted away from the head during the cutting process. When hair is elevated at 180 degrees, it is lifted straight up, or 'overdirected', to the opposite side of the head from where it naturally falls. This technique is generally used to create layers that are shorter on the top and longer towards the bottom, giving the final haircut more volume and movement. The elevation of the hair influences the gravitational force on the hair, which is essential for achieving the desired layering effect and blending the lengths seamlessly.