A mounting device or bracket for paneled building surfaces is disclosed. The mounting bracket includes an upper wall in the form of a flat surface for supporting various types of attachments. An elongated mounting slot extends through the upper wall, and the mounting bracket includes an elongated nut receptacle that is positioned below this elongated mounting slot. With an attachment being positioned on the upper wall, an attachment fastener may be directed through the attachment, then through the elongated mounting slot, and then may be threadably engaged with a nut that is positioned within and movable along the nut receptacle in its elongated dimension. The elongated configuration of the mounting slot and nut receptacle provides adjustability for the position of the attachment fastener relative to the mounting bracket, including after the mounting bracket has already been installed on the building surface.