Ladder trays, with their two side rails connected by rungs, are the most common type. This design is ideal for power cables and. (1) Natural Airflow: We use the natural way hot air rises and cool air falls due to temperature differences inside and outside to cool the cable trays. (2) Forced Airflow: Sometimes, we use. The cable tray types to choose from are ladder, ventilated trough, or solid bottom. What are the reasons for selecting a specific type of cable tray? The engineer or designer should select the type of cable tray that has the features which best serve the project's requirements. Type MI cable is an excellent cable for critical circuits.