Many components in distribution and control equipment are designed for easy installation into equipment by having a recess and retaining clip on the rear surface; all switch handles and indicators are on the front face. This allows the item to be clipped onto industrial standard symmetrical DIN rail. The devices can be fitted to and removed from the rail very easily. No mounting holes or covers need to be drilled or cut. The front covers have access slots to allow the devices to be operated but shroud all terminals and other live parts. This arrangement allows equipment to be quickly built up either in the workshop or on site with the minimum of tools and time. Enclosures are available to suit most environments and operating conditions: in steel or plastic material, with ingress protection from IP30 to IP66. Enclosure capacities are measured in modules of 18mm width. There may be one or more rows for devices