A cable tray joint plate is a flat metal piece used to join two cable trays. It comes with drilled holes for nuts and bolts. It is used in a range of applications with sp nch runs from the main cable tray system to electr cal devices or other equipment. A complete system is made up of. A cable tray is a unit, or set of units, with their fittings forming a rigid structure to support cables and assist in channeling them. As cables and trays expand or contract, they can cause stress on the structure, leading to potential damage or misalignment.