Bulletin board advertising involves finding a bulletin board in a public or private space and attaching information about your service or product to it. Depending on the location and what you're marketing, this can be a fairly beneficial advertising tool.
College campuses or in employee break rooms often have bulletin boards where people advertise concerts, club meetings, various lessons and missed connections. Some advertisers completely cover the board and everything that's already been posted on it, but this practice is generally frowned upon. Bulletin boards are mainly used for smaller businesses and organizations, so an organization may outgrow the usefulness of this method of advertising.