A hammer is the simplest of tools, but it is mighty. There is a powerful inevitability to a hammer at its apex, poised in midair, an extension of your arm, milliseconds from pounding metal or stone or wood with the strength of fifty men. Once, long ago: a stone lashed to a stick. Today: all manner of specialized forged-steel heads on ergonomic handles, a hammer for every job. (Photographs by Ben Goldstein.)