Masons'' marks, the ciphers made by stonemasons on the fabric of buildings, exist for practical reasons, and have been in use for over 4 000 years. For much of the period the marks stood outside literacy and acted as a mechanism for the transmission of instruction that while simple in operation, draws on a sophisticated system of visual signs used more widely elsewhere. This is the first book on the subject and it provides a historical overview as well as an analysis of the topic, establishing the origins and demonstrating the development of systems of non-literate forms of communication in the stone-building industry. The book is a pioneering study of a little understood topic and while the focus is on British buildings, examples are drawn from further afield to widen and inform the debate. Study of the marks, using methodologies developed from archaeology, provides innovative ways of understanding the construction of buildings, and of the working methods of medieval stonemasons. Beyond the medieval period it represents a completely new approach to the study of country houses in Britain, and demonstrates the study of marks to be a powerful new methodology with the potential to reveal a great deal of new information about the ways in which houses, and also industrial buildings were constructed. This book is aimed at academic architectural historians and people professionally engaged with the historic built environment such as archaeologists working on standing buildings, and conservation architects. It will also be useful to students at undergraduate and postgraduate level on courses in architectural history, and it would appeal to owners or guardians of historic buildings, members of organisations like English Heritage and the National Trust, members of Freemasons'' Lodges, and the general reader with an interest in the means by which the great buildings of the past were constructed, or indeed parish church enthusiasts whose buildings contain marks. Recording of masons'' marks has been undertaken in Europe including Scandinavia, in particular in Germany and the Low Countries, and the book would have an international appeal.