Charles Ellicott Commentary Nehemiah 3:15

"And the fountain gate repaired Shallun the son of Colhozeh, the ruler of the district of Mizpah; he built it, and covered it, and set up the doors thereof, the bolts thereof, and the bars thereof, and the wall of the pool of Shelah by the king`s garden, even unto the stairs that go down from the city of David." — Nehemiah 3:15 (ASV)

He covered it. —Similar to laid the beams in Nehemiah 3:3; Nehemiah 3:6.

The pool of Siloah. —Called before “the king’s pool,” which received its water as “sent” through a long subterranean conduit, and supplied the king’s gardens.

The stairs. —Down the steep sides of Ophel, of which traces are thought still to remain. From this point it is very hard to trace the exact course.