Hold-Down side secures and prevents lateral movement of cable tray while expansion side allows for thermal expansion and contraction of cable tray. For extremely corrosive applications we offer a full line of straight sections, fittings, covers and mounting accessories in polyester and vinylester fiberglass. Rail heights are available in 4"" and 6"" and widths are available up to 36"". Designed for use with all trays. Type GBM high. The Hold Down Package consists of the necessary components for securing Cope-GLAS tray to strut or wall brackets. Gratemetal Hold down clamps or Z.