Abstract: A ceiling construction for demonstration equipment comprises a number of rectangular panels which between them define guide slots for a sliding link chain which will carry samples. The panels are supported by parallel rails which carry undercut longitudinal grooves on their lower sides for the receipt of clamping elements carried on the upper surfaces of the panels, the disposition of the grooves and clamping elements being such as to maintain a desired width along the length of the slots. Adjacent panels may be spaced as required in the longitudinal direction of the grooves by longitudinally positioned spacing pieces positioned in the grooves.