Cable tray support quantity can be calculated using a simple formula: Support Quantity = Total Length ÷ Support Spacing + 1 20 ÷ 2 + 1 = 11 supports In a typical project, a 20-meter cable tray with 2-meter spacing requires 11 supports. This publication is intended as a practical guide for the proper and safe* installation of cable ladder systems, cable tray systems, channel support systems and associated supports. The system allows the use of electrical resources in electrical installations and/ or in communication systems.