Boundary is a central concept and mechanisms in semiotics (of culture). Resulting from the appearance of discreteness, it is present already at the elementary level of semiosis. The boundary can be defined as a spatializing distinction. As such it is a structural feature of spatial modelling – for example, a central feature for Juri Lotman’s models of ‘text’, ‘cultural space’ and ‘semiosphere’, but in contrast curiously not present in others, e.g. in Pierre Bourdieu’s ‘social space’ as focused on social-cultural distinctions. It is also present in the sociocultural semiosis itself. Identifying empirical semiotic boundaries can however be problematic – rather than structural features they exist in the process of distinction making and by applications of distinctions. Therefore, I aim to relate the notion of boundary, including its elementary and theoretical nature, to ‘boundary signs’ and their modalities as manifestations and evidence of semiotic boundaries, and to the objectivation process of boundaries whereby specific and particular distinctions become widely shared, institutionalised and comprehensible across cultural differences and over history. Explication of the process of objectivation and modalities of ‘boundary signs’ enables the shift of ‘boundary’ from theoretical semiotic notion to a methodological tool for the semiotic analysis of traces of cultural change and of interrelations of semiotic systems.