Cable ladder is one of the most widely used in industrial and civil buildings. It has the advantages of light weight, large load, beautiful appearance, simple structure and convenient installation. It is suitable for both the installation of strong electric cable of small diameter and the laying of weak electric cable. In the project, there are two ways of laying the tray with or without a cover. The tray without a cover has good heat dissipation performance, but it is easy to fall dust, and troublesome to clean. It is usually used in dust-free or less dust places, otherwise the tray with a cover should be used. Tray selection principles are as follows: A: Tray can be used for wiring of ordinary power cables and communication cables, but tray without covers are not allowed to be laid in the ceiling or hanging ceiling; B; 750°C, 1.5 h refractory cable can be wired with covered tray, (the tray shell should be made of fire prevention materials.)