Folklorists divide customs into several different categories. A custom can be a seasonal celebration, such as Thanksgiving or New Year's. It can be a life cycle celebration for an individual, such as baptism, birthday or wedding. A custom can also mark a community festival or event; examples of this are Carnival in Cologne or Mardi Gras in New Orleans. This category also includes the Smithsonian Folklife Festival celebrated each summer on the Mall in Washington, DC. A fourth category includes customs related to folk beliefs. Walking under a ladder is just one of many symbols considered unlucky. Occupational groups tend to have a rich history of customs related to their life and work, so the traditions of sailors or lumberjacks. The area of ecclesiastical folklore, which includes modes of worship not sanctioned by the established church tends to be so large and complex that it is usually treated as a specialized area of folk customs; it requires considerable expertise in standard church ritual in order to adequately interpret folk customs and beliefs that originated in official church practice.