This dissertation is the first systematic investigation of the materiality of Safaitic inscriptions, which were carved by ancient nomads in the Ḥarrah, a basaltic desert stretching from southern Syria, through north-eastern Jordan, into northern Saudi Arabia. The thesis focuses on graphic variation and palaeographic development in the Safaitic inscriptions, seeking to analyse different levels and patterns of variation in the Safaitic script(s). By using the long genealogies of several texts by members of the lineage of Ḍf as chronological framework, it describes and measures the palaeographic development from the ‘common’ to the ‘fine’ script across generations. In addition, the information from the Ḍf lineage-tree and the attested generations is combined with the dated texts by members of the same lineage in order to provide a working chronological framework for Safaitic writing among the Ḍf. The thesis also deals with other aspects of the materiality of Safaitic texts which have never been treated systematically, such as carving techniques, text layout, writing styles, and disruptive practices towards the texts, that is, their effacement and modification.