A builder

"The Builders are carpenters, masons, miners, and woodsmen, tasked with maintaining the Wall as well as its barriers, keeps, towers, and structures, which have fallen into disrepair over the years."
―Lord Commander Jeor Mormont.[src]

Builder is a position within the Night's Watch. They are tasked with maintaining the Wall and its defenses as well as the castles and keeps of the order. Jon Snow claimed that a small patrol of Builders, with a pair of Rangers for defense, regularly survey the top of the Wall to check for structural damage. 

​All Builders report to the First Builder, who in turn reports to the Lord Commander of the Night's Watch.

Prominent Builders