Saddle querns, consisting of a rounded handstone and a saddle-shaped grindstone, were used to crush or remove the outer skin of berries and grains. The berries or grains were placed on the grindstone, and then the handstone was rolled over them back and forth using both hands, like a rolling pin. From the beginning of the Neolithic period, saddle querns were used to process nuts, such as acorns. With the advancement of agriculture, these tools gradually came to be used to process grains as well. Handstones could also be used for other purposes, including as a pestle for grinding grain in a mortar, or as a hammer for making stone tools or breaking open clam shells.