Since these men are Nehemiah’s personal staff, we might best picture them as serving in a supervisory role over the building crews, responsible for reporting to Nehemiah what was happening on the ground. Nehemiah assigned half of his staff to this task. Perhaps that is in distinction from his entire staff having performed this function previously.
16 From that day on, half of my servants worked on construction, and half held the spears, shields, bows, and coats of mail. And the leaders stood behind the whole house of Judah,