Drill the drill holes with ∅ ≥ 7 mm in the tray rail and tray base. To avoid transverse bending at higher loads, a joint plate must be used for tray widths of 400 mm or more in the joint area of the cable trays that are to be connected. Important design note - Unlike ladder and ventilated cable trays, solid bottom cable trays can collect and retain moisture. Install spring n ts in strut portion of center hanger. 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. us-trations without notice. The mechanical and electrical characteristics, tests, certifications, overall quality management, recommendations mentioned. But before you lay the first tray or clamp down a single cable, you need a solid plan.