The Wall is by default placed in an event or group page (located at the bottom of the page). The Admin does have the ability to hide the wall from users.

If the wall exists, any user is able to post a message onto the wall.

As of today, when someone posts a message onto the wall, only the admin is notified of the wall post, but the post is displayed publicly for consumption of other members. 

Below is an example of the wall: 

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