It?s been four years since international business consultant Todd Bol constructed a wooden replica of a one-room schoolhouse, filled it with books, and mounted it on a post in his front yard in a suburb of metropolitan Minneapolis, Hudson, Wis., in tribute to his late mother. A sign urged passersby to take free books or else leave books. Today, Bol and Rick Brooks, an instructor at the University of Wisconsin in Madison, head up the nonprofit organization Little Free Library, which promotes literacy through both sales and donations.