Barrier

A Barrier is a feature present in every zombie map except for, in very rare cases, some fan fiction maps, like Lockdown. Barriers act as way for the zombies to get into the map. They must first break down the barrier before getting in, allowing the players a chance to kill them before they enter, or at least slow the zombie down. They can be also be repaired, and you get 10 points for each part of the barrier to repair. There are severel different types of barriers.
 * Standard - These barriers typically have 6 parts to them, almost always being boards. Sometimes, like in Ascension, it might have something different then boards, like metal bars.
 * Walls - Sometimes zombies will make a whole in the wall to break through. While these are less noticeable, they also have more pieces for the zombie to break away and the player to rebuild.
 * Window - This one's only canon appearance is in "Five". These are the only canon barriers the player can break. While they may be glass, it is repaired with boards, so once all the glass is gone it will basically be a standard barrier again.