The drug design process is a multi-stage process. Particularly in later drug design stages, it is desirable to fix a molecule to a known core sub-structure or "scaffold" and explore different decoration groups. Or alternatively, to fix certain periphery sub-structures or "fragments" and explore chemical sub-structures to combine them together, known as fragment linking, or scaffold hopping. Such chemically constrained modification has useful applications, for example, to tweak molecular properties of a lead series, to combine two weakly binding fragments identified through fragment-based campaigns , to optimise proteolysis targeting chimeras that link two warheads , or to quickly identify novel intellectual property .