Transformation optics has recently emerged as a powerful and systematic approach to design application-oriented metamaterials. In this letter, following up on our previous studies on thin planar retroreflectors, we show how it is possible, in principle, to design ``transformation medium’’ coatings capable of controlling the scattering response of metallic corner- and wedge-type structures so as, e.g., to strongly enhance the specularly reflected component. We validate our results via a full-wave study of the near- and far-field responses, and envisage possible applications.