Ceilings or walls

Claim 1

A CEILING COMPRISING A STRIP-METAL GRIDWORK HAVING RECTANGULAR OPENINGS, A PLURALITY OF RECTANGULAR CEILING PANELS REMOVABLY SUPPORTED ON SAID GRIDWORK WITH EACH RECTANGULAR OPENING IN SAID GRIDWORK BEING CLOSED BY ONE OF SAID PANELS, SAID PANELS EACH COMPRISING A RECTANGULAR METAL FRAME WITH AN OUTWARDLY PROJECTING LOWER PERIPHERAL FLANGE EXTENDING CONTINUOUSLY AROUND SAID FRAME AND FORMING A LOWER SURFACE, THE PORTIONS OF SAID FLANGE ON OPPOSED SIDES OF SAID RECTANGULAR FRAME EXTENDING OUTWARDLY IN THE SAME PLANE IN OPPOSITE DIRECTIONS, A SHEET OF FLEXIBLE SYNTHETIC PLASTIC MATERIAL EXTENDING ACROSS SAID LOWER SURFACE OF SAID FRAME IN A STATE OF TENSION, A THICKENED SYNTHETIC PLASTIC BORDER EXTENDING CONTINUOUSLY AROUND THE PERIPHERY OF SAID SHEET AND CONTAINING A CONTINUOUS GROOVE WHICH OPENS IN A DIRECTION PARALLEL WITH SAID SHEET AND IS DIMENSIONED TO RECEIVE SAID FLANGE, THE PORTIONS OF SAID CONTINUOUS GROOVE WHICH EXTEND ALONG OPPOSITE EDGES OF SAID SHEET OPENING TOWARDS EACH OTHER, SAID CONTINUOUS FLANGE BEING RECEIVED IN SAID CONTINUOUS GROOVE IN THE BORDER OF SAID SHEET, SAID SHEET OF FLEXIBLE SYNTHETIC PLASTIC MATERIAL AND SAID THICKENED BORDER PORTION THEREOF BEING READILY REMOVABLE FROM SAID FRAME AND HAVING AN INHERENT ELASTICITY WHEREBY SAID SHEET MAY BE STRETCHED ACROSS SAID FRAME AND SAID GROOVED BORDER PORTION SNAPPED ON TO SAID LOWER PERIPHERAL EDGE OF SAID FRAME.