Fore-and-aft

Aligned with or running approximately parallel to a vessel’s centreline.

The expression describes an orientation along the length of the vessel rather than across it. Fore-and-aft movement, structure or rigging therefore runs generally between bow and stern, while an athwartships direction runs from side to side.

It is also used in sailing terminology. A fore-and-aft sail is set broadly along the vessel’s centreline and can be trimmed on either side, unlike a square sail whose principal supporting yard lies across the vessel.