Spindle whorls are the most basic type of tools that were used to twist fibers into thread. A stick was inserted into the central hole of the spindle whorl, to serve as the axis; then, fibers were attached to the stick, and the spindle whorl was spun so that the fibers twisted together. Notably, excavations at a shell midden site in Dongsam-dong, Busan uncovered a pottery shard that was imprinted with a fish net, showing that ancient fish nets were made by twisting together two or three strands of thread. Most spindle whorls of the Neolithic period are made of clay and are about 4 to 5 cm in diameter. They come in a variety of shapes, including conical, bead-shaped, and disc-shaped.