We met this man previously, in Nehemiah 3:4. Apparently, after he had completed work near the Fish Gate (on the city’s north wall), he volunteered to do a (short) piece on the east side, specifically the section from the door
of Eliashib’s house to the end
of his house. While that is (probably) a relatively short section, we need to bear in mind that the topography of the city of Jerusalem fell away sharply into a ravine on its eastern side. That would make retrieving the fallen stones a major challenge. That also explains why there are more volunteers labouring on the eastern wall than on the western.
21 After him Meremoth the son of Uriah, son of Hakkoz repaired another section from the door of the house of Eliashib to the end of the house of Eliashib.