Set-in sleeves are a type of sleeve construction where the sleeve is sewn into the armhole of a garment, creating a smooth and tailored look. This design allows for a natural fit around the shoulder and arm, making it a popular choice for many types of clothing, including shirts and dresses. The set-in sleeve is typically cut separately from the body of the garment and is attached after the main pieces are assembled. This method provides more structure and can enhance the overall silhouette of the garment, contributing to a polished appearance.