Crime Prevention Through Environmental Design (CPTED), was the description invented by the criminologist C. Ray Jeffery in his book of the same title (1971). It was originally described as a multi-disciplinary approach to deterring criminal behaviour, delivered through the implementation of changes to the built environment. In essence, CPTED strategies concentrate on the capacity to influence offender behaviour, before they reach the target in question and as a means to dissuade them from committing criminal acts. Meanwhile, recent decades have witnessed both the evolution of research, findings and theories detailed in Chapter 2, Evidence from Crime Science. And new manufacturing techniques, standards and testing (most especially in relation to doors and windows - see Chapter 7) have made it more physically difficult for the criminal to gain access once he reaches the fabric of the building. This Chapter is specifically dedicated to the Physical Security 'Target Hardening' Measures, Technological Innovations and Environmental Elements of CPTED.