Formal theories of design have described design as a quest for the fit between two spaces such as form-context, solution-problem, structure-function and presently Technology-Environment (T-E). On the contrary, existing methods tempt to focus on E; most engineering disciplines serve T; designers are consequently left barehanded to apply formal principles. More specifically a design method should help to overcome design fixations and enable to steer T-E double exploration. First we extend Concept-Knowledge formalism by defining the inverse C-K of a considered C-K, i.e. the knowledge base is put into question to formulate a new initial concept and the initial concept has an assumed logical status to become the new knowledge base concept. In this configuration, one C-K can benefit from expansions of the other. Second a method is deduced by applying this principle to the T-E framework: designers should steer their exploration by drawing simultaneously T C-K and E C-K. Four empirical cases are analysed. The results suggest that the method enables to identify a maximum of fits before converging on one when used from the start or can provide defixating knowledge expansions when not.