A running in board is a large sign showing the name of the railway station on which it is found. The signs are intended to help passenger

Passenger

A passenger is a term broadly used to describe any person who travels in a vehicle, but bears little or no responsibility for the tasks required for that vehicle to arrive at its destination....

s discover their location when on a train

Train

A train is a connected series of vehicles for rail transport that move along a track to transport cargo or passengers from one place to another place. The track usually consists of two rails, but might also be a monorail or maglev guideway.Propulsion for the train is provided by a separate...

 entering the station, possibly while still moving at speed.

In normal circumstances a two platform through station has one running in board on each platform situated near that end of the platform which trains serving the platform run in to - hence 'running in board'.

During the Second World War, running in boards in the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 were removed or obscured to prevent enemy spies

Espionage

Espionage or spying involves an individual obtaining information that is considered secret or confidential without the permission of the holder of the information. Espionage is inherently clandestine, lest the legitimate holder of the information change plans or take other countermeasures once it...

 or paratrooper

Paratrooper

Paratroopers are soldiers trained in parachuting and generally operate as part of an airborne force.Paratroopers are used for tactical advantage as they can be inserted into the battlefield from the air, thereby allowing them to be positioned in areas not accessible by land...

s from easily discovering their location.