Final answer:
Hair projected below 90 degrees builds weight, creating a heavier and fuller look.
Step-by-step explanation:
When hair is projected below 90 degrees, it is being cut at an angle that creates weight in the hair. This technique is commonly used in the field of cosmetology to add volume and density to the hair. By cutting the hair below 90 degrees, the stylist can create a solid base at the ends, giving the hair a heavier and fuller look.