Planning processes in medieval and early modern European technology have not yet been comprehensively studied. The aim of my project is to take stock of planning processes described in passing in the secondary literature, to set up an interpretative framework, and to develop an agenda for future research. The project is thus devoted to forms of knowledge that were of crucial importance to “making technology work” in medieval and early modern Europe, but have often been disregarded by historical actors as well as by modern researchers as they are much less spectacular than heroic invention or the emergence of technical sciences.