This working paper develops the methodological foundation of Registertopologie as an analytical model of operative stabilization within the broader framework of Philosophie der Schwelle (Philosophy of the Threshold). It defines Operationsarrangements as minimal structural configurations in which differences are articulated, effects emerge, and stabilization occurs through inscription. Stability is conceptualized as the integration of structural non-fit. On this basis, the paper unfolds the interrelated concepts of effect, inscription, register, institutionalization, and mesenchymal differentiation as moments of an operative architecture. The model clarifies the structural conditions under which differentiation becomes durable, historically effective, and normatively extended. Registertopologie functions as a methodological explication of the ontological framework developed in Philosophie der Schwelle. This paper constitutes the first installment of a three-part working paper series dedicated to the systematic development of Philosophie der Schwelle.