A thimble is a bell or ring shaped sheath with a hard substance, such as bone, leather, metal or wood. It is worn on the tip or middle of a finger or thumb to help push a needle while sewing and to protect the finger/thumb from being pricked. Many thimbles are pitted to help hold the needle in place. Thimbles made of precious stones, mother-of-pearl, glass or porcelain are usually for decorative, rather than functional purposes.