Cable ducts, which are also known as trunking, are hard boxes that are used to conceal the wires and prevent them from being dusted or touched by people. They are optimal in the office, in schools, or in clean rooms where everything has to be seen as looking clean and tidy. Cable trays are designed to accommodate a large number of cables while allowing for easy installation, modification, and maintenance. Types of Cable. While the choice largely depends on the environment and volume of cabling, the most commonly used systems fall into three main categories: cable trays, cable trunking, and conduits. People worry about which system is safer, more cost-effective, and easier to install.