Site recording of historic engineering works can be considered as a form of preservation since the results of such an industrial archaeological study provide the building blocks for historians concerned with all aspects of the history of technology and historic preservation. The emphasis of this discussion is on fundamentals rather than on details of recording techniques. The subject is introduced with an examination of how the historian evaluates historical facts. The idea, however, that primary source material is obtained from archival records only, must be expanded to include a wide range of archaeological evidence obtained from studying a specific site. Unlike more traditional approaches to recording historic architectural structures, engineering and industrial sites often involve dynamic processes as well as static structures and machines. Thus establishing what to record is discussed in terms of available recording techniques and the historic significance of the site. The fundamentals of preservation through recording are illustrated by two selected case studies.