Abstract: Methods for installing a door assembly in a rough opening at a job site include performing the following steps at a location remote from the job site where the door is to be installed: positioning a door frame around a perimeter edge of a door panel; attaching the door panel to the door frame with a plurality of hinges to comprise a pre-hung door; retaining the door frame square with respect to the door panel; attaching a plurality of mounting brackets to the pre-hung door. The method also includes inserting the pre-hung door into the rough opening at the job site and attaching the mounting brackets to the rough opening to support the door panel for opening and closing before the door frame is attached to the rough opening.