Unsourced material may be challenged and removed. They are especially useful in situations where changes to a wiring system are anticipated, since new cables can be installed by laying them in the tray, instead of pulling them through a pipe. Several types of tray are used in different applications. A solid-bottom tray provides the maximum protection to cable tray types pdf, but requires cutting the tray or using fittings to enter or exit cables.
A deep, solid enclosure for cables is called a cable channel or cable trough. A ventilated tray has openings in the bottom of the tray, allowing some air circulation around the cables, water drainage, and allowing some dust to fall through the tray. Small cables may exit the tray through the ventilation openings, which may be either slots or holes punched in the bottom. Ladder and ventilated trays may have solid covers to protect cables from falling objects, dust, and water.