How can I securely hang a heavy mirror using a wooden French cleat?

To securely hang a heavy mirror using a wooden French cleat, first, attach one part of the cleat to the back of the mirror and the other part to the wall. Make sure the cleat is level and securely anchored to the wall studs. Then, simply hang the mirror on the cleat, ensuring it is properly aligned and supported. This method provides stability and security for heavy mirrors.