Abstract: A display sign of box-like construction has internal illumination and a face comprising a transparent or translucent sheet with advertising material applied thereto. The face is tensioned by means of a locking element to which the face is attached and which is then forced into the gap between two surfaces. The element is serrated and one of said surfaces includes a detent which co-operates with the serrations. The pull exerted by the tensioned face pulls the locking element into a position in which it lies skew to said surfaces and bears on both said surfaces with the detent between adjacent serrations. There can be one or more locking elements along each edge of the sheet, or one or more locking elements along one edge of the sheet only. The sheet can be tensioned by locking elements acting in two directions which are at right angles to one another.