On a German building site, the site manager or supervising architect keeps a Bautagebuch, a construction diary. It records each day’s workers and machines, deliveries, weather, obstructions, inspections and defects found, and when and how they were put right. A building trade publisher calls it eine Hauptleistungspflicht des Bauleiters bzw. überwachenden Architekten, one of the main duties of the site manager or supervising architect. Its value lies in later disputes. Gaps in the record can as a rule not be filled in afterwards.