Originating in rural American in the 18th century, barn raisings were an occasion where a community would turn out to help construct a barn for one of its members. The workers were unpaid, but with the understanding that the favor would be returned to them in the future. It was considered mandatory, and missing a barn raising in your community was a sort of social faux pas. Children would gather around to watch and learn about what would be expected of them when they grew older. Young men provided heavy labor and more experienced and elderly workers provided leadership. Women toiled to provide food and drink to the many workers.
Today, some Amish and Menonite communities still hold barn raisings, though they pretty much halted in the rest of the country by the end of the 1800's. However, you'll still find such a thing from time to time among friends, especially in the rural northeast.
Have you ever participated in a communal work day, either by hosting or by helping? If you hosted, was the favor eventually returned to those who helped you? If you helped, was the favor returned to you?