This is a simple one really. It is anything that is placed perpendicular to the centerline of the ship. It is almost always used to refer to any of the passage ways that run across the ship. The main deck of a ship is several athwart ships passageways. These run from one side to another and mostly are butted up to a watertight bulkhead. Having this set up allows for fire teams to cross the ship and not have to break water tight integrity.

Most athwart ships passage ways are not blocked by any type of door. Since they are on the main deck above the waterline this is not required. But even with this being said on our ship the passageway just forward MER1 and next to the ships store had a regular style door in it. Why was that? I have no idea.

Pretty simple one for today.