Albert Barnes Commentary 1 Kings 7:5

"And all the doors and posts were made square with beams: and window was over against window in three ranks." — 1 Kings 7:5 (ASV)

All the doors and posts - The doorways, and the posts that formed them, seem to be what is meant. These were square at the top, not arched or rounded. In Assyrian buildings, arched doorways were not uncommon. The doorways, like the windows, also faced one another exactly.