Abstract: In a ceiling comprised of rectangular metal ceiling panels each having a perforate face panel and an imperforate back panel spaced from one another, the side and end margins of the face and back panels being defined by the bend of lips integral with the panel, the lips of face and side panels being joined to form side and end walls, the end walls are provided with an inverted, open-mouthed channel, offset inboardly with respect to the back panel and intermediate the height of the end wall between the face and back panel, and the side walls of contiguous ceiling panels are provided with an outwardly opening cove along one panel and an outboardly projecting tongue in the contiguous panel.