Final answer:
Arc-based pin curls are also known as sculpture curls or flat curls. They are created by winding the hair in a flat, ribbon-like shape around the finger and securing it to the scalp with a bobby pin or clip.
Step-by-step explanation:
Arc-based pin curls are also known as: sculpture curls or flat curls. They are created by winding the hair in a flat, ribbon-like shape around the finger and securing it to the scalp with a bobby pin or clip. This technique creates tight, defined curls that lie close to the head, making it a popular choice for vintage hairstyles.