羊皮纸, or "parchment," is a writing material made from the skin of animals, typically sheep, goats, or calves. It has been used for centuries as a durable surface for writing and is known for its smooth texture and ability to hold ink well. Parchment was commonly used in ancient manuscripts and important documents. The process of making 羊皮纸 involves cleaning, stretching, and drying the animal skin. This method results in a strong and flexible material that can last for many years. Today, 羊皮纸 is still used in art, calligraphy, and for creating high-quality documents, preserving its historical significance.