Charles Ellicott Commentary 2 Chronicles 8:5

"Also he built Beth-horon the upper, and Beth-horon the nether, fortified cities, with walls, gates, and bars;" — 2 Chronicles 8:5 (ASV)

Also. — And. 1 Kings 9:17, And Solomon built Gezer, and Beth-horon the nether.

Built — that is, fortified, as the rest of the verse explains. (See 1 Chronicles 7:24.) He built them as (or into) fenced cities, namely, walls, doors, and bar (Micah 7:12; Deuteronomy 3:5). This description is lacking in Kings.