To protect a ceiling finishing material, to prevent falling, to accelerate and simplify construction and to lower costs by increasing strength of a junction against horizontal and vertical vibrations of a base assembly such as a ceiling joist assembly assembled in a lattice shape.

A joint metal comprises a pair of two sidewalls put on and joined from an upper part of a base assembly member to be joined, and is longitudinally, horizontally and vertically fastened in a three-dimensional manner with nails or machine screws from a side face to the base assembly members gathered at a junction. By using the joint metal of the invention, the strength of the junction is increased, construction is simplified without the need of skilled technique at the same time, and costs are reduced by utilizing short-length materials and reducing waste or the like.