This article looks at some of the metaphysical properties of cognitive artefacts. It first identifies and demarcates the target domain by conceptualizing this class of artefacts as a functional kind. Building on the work of Beth Preston, a pluralist notion of functional kind is developed, one that includes artefacts with proper functions and system functions. Those with proper functions have a history of cultural selection, whereas those with system functions are improvised uses of initially non-cognitive artefacts. Having identified the target domain, it then briefly looks at the multiple usability of physical structures and the multiple realizability of cognitive function. Further developing insights from the "dual nature of artefacts thesis", the article ends with conceptualizing the structure-function relations of cognitive artefacts. More specifically, it unpacks the relation between physical structure, representational structure, information, and cognitive function.