Late Britain is a Left 4 Dead 2 campaign which brings a British environment into play; rather than an American city or town filled to the brim with weapons, the survivors will find themselves using what they have in a world with almost no firearms at all.
The wooden wall is normally fully solid, and can be damaged by the infected team to show a hole, through which Boomers, Smokers and Spitters can attack through.
The wall may be completely broken once damaged, allowing an extra entrance/exit for other infected, like this charger, to attack through.