Part B of the VOB is a set of standard terms for German construction contracts. Its Section 4 divides the roles on the site. The client hat das Recht, die vertragsgemäße Ausführung der Leistung zu überwachen, has the right to monitor that the work is carried out as agreed. He may give orders that are needed for this. But he must give them unter Wahrung der dem Auftragnehmer zustehenden Leitung, while respecting the contractor’s right to manage the work. As a rule, he gives such orders only to the contractor or to the contractor’s appointed site manager. The exception is imminent danger.
Section 4 (2) describes the contractor’s side. Der Auftragnehmer hat die Leistung unter eigener Verantwortung nach dem Vertrag auszuführen. The contractor must carry out the work under his own responsibility, according to the contract. Es ist seine Sache, die Ausführung seiner vertraglichen Leistung zu leiten. It is his business to manage the execution of his work.