Cable trays are like special roads for wires. They keep cables organised, supported, and protected. But if you don't use these “roads” properly, you run into trouble. Too many wires crammed. This guide will walk you through the simple, clear principles for getting cable trays wiring right. It acts as a dedicated pathway for power distribution and data transmission, often supporting cables hidden behind walls or above ceilings. Fill Rules for Single-Conductor Cables 4. A rung spacing of 6 to 9 inches (150 to 230 mm) is preferable when the cable tray cont d for instrumentation and control applications that require. In the electrical wiring of buildings, a cable tray system is used to support insulated electrical cables used for power distribution, control, and communication.