Before any wiring system is installed, account must be taken of the environment in which the system is to operate. There are many influences that may contribute to the final design of the installation. The IET Regulations employ an alphanumeric system with three categories: environment, utilization of the environment and the building structure. Polyvinyl chloride (PVC)-insulated single-core cables (singles) are used when the installation is to be run in conduit or trunking. The insulation immediately surrounding a cable conductor is designed to withstand the cable’s working voltage in order to prevent danger. The uses of plastic materials (polymers) in electrical engineering are widespread, the most common being for cable insulation. As tools play an important part in installation work, it is perhaps sensible to understand some of the processes involved in their manufacture. This applies particularly to hardened, tipped tools such as chisels, drills, scribes and so on.