What is the meaning of Gangboard?

A board or plank used as a temporary footbridge between a ship and a dockside or any gap such as scaffolding.

A board or plank placed within or without the bulwarks of a vessel's waist for lookouts to walk or stand on.

The boards ending the hammock-nettings at either side of the entrance from the accommodation-ladder to the deck.

Source: wiktionary.org