The design and the making of mouldings in historic architecture is a good example of how complex relations of geometric features to semantic ones can be. Can architects who deal with historic artefacts, and who practice with computer solutions from the engineering world, still handle knowledge before handling geometry? This paper presents two very different case studies through which comprehensive analysis/modelling /representation processes have been implemented. In a converging conclusion, it introduces a visual codification of mouldings. The contribution underlines the benefits of implementing a robust theoretical model of mouldings in the analysis of historic artefacts, notably in order to facilitate comparative dating, survey operations, typology analysis.