One end of the hammer's head is used to hammer nails. The opposite end can have various purposes, one of which is hammering a metal surface. In this case, this part of the hammer is rounded, and known as the pein or peen. Peening is the process of working a metal surface by hammering.
In a claw hammer, one end of the head is shaped as a claw for pulling out nails.
In a club hammer, the two ends of the head tend to be identical. A club hammer is essentially a small sledgehammer, for driving chisels or stakes.
© Haydn Thompson 2021