Ball-pein, or ball-peen, hammers are also known as "machinist's hammers." The hammer has a spherical head known as the "peening face," which is used rounding off edges and smoothing surfaces. The opposite end of the hammer is flat, and is used for striking surfaces. With the development of technology, the use of ball-pein hammers has become less common in manufacturing. The hammers are still, however, frequently used by artists.