Cable trays are above-ground systems that support and organize cables. The biggest difference is how they're installed—trays are exposed, trenches are buried. While they serve the common purpose of routing and securing cables, these systems differ in design, application, installation, and. maintain spacing or to keep cables in place when the tray is ect the minimum bend ra-dius for cables as they exit the bottom of the cable tray. Some versions have small holes in the bottom. This helps with cable ventilation to manage heat. NEC section 300-8 does not permit any tube, pipe, or equal for water, air gas, drainage, steam, or any service other than electrical in raceways or cable trays containing. Cable trays support insulated electrical cables in industrial and commercial settings.