A surveyor's assistant who holds and operates the measuring chain during land surveys.
From English 'chain' + 'man' (from Old English 'mann'). The term became standard in surveying profession during the 18th-19th centuries.
Chainmen were the frontline heroes of mapping—they literally blazed trails through wilderness, and many cities we know today were first outlined by a chainman pulling a metal line through unmapped territory.
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