What does a ball peen hammer typically have on its head?

A ball peen hammer is characterized by its unique design that includes a rounded face on one end of its head. This rounded face is specifically intended for shaping metal, as it allows the user to apply force to create curves or to "peen" the surface of the metal to work-harden it. In contrast to the flat face of a typical hammer, which is used for driving nails or providing a flat impact, the rounded face of the ball peen hammer provides versatility in metalwork, making it a crucial tool for tasks like forging or metal shaping.

The other options represent features of different types of hammers or are variations that do not apply to a ball peen hammer. For instance, the flat face is commonly associated with claw hammers or sledgehammers, while a chisel edge would be more applicable to chiseling tools rather than hammers. A cross-peen head is a feature of a different hammer designed for specific types of work, such as joinery or stonework, and is not a standard characteristic of a ball peen hammer.