Framework for a suspended ceiling

Claim 1

IN A SUSPENDED CEILING COMPRISING A LONGITUDINAL SUPPORT MEMBER AND A PAIR OF COLLINEAR TRANSVERSE SUPPORT MEMBERS INTERSECTING SAID LONGITUDINAL SUPPORT MEMBER WHEREIN EACH OF SAID SUPPORT MEMBERS COMPRISES A VERTICAL WEB HAVING OUTWARDLY EXTENDING CEILING-PANEL-SUPPORTING FLANGES, AND WHEREIN SAID LONGITUDINAL SUPPORT MEMBER HAS AN OPENING IN THE VERTICAL WEB THEREOF, THE IMPROVEMENT WHEREIN SAID OPENING COMPRISES A VERTICAL SLOT AND AN INCLINED SLOT, AND AN INTERMEDIATE AREA JOINING THE UPPER END OF THE INCLINED SLOT WITH A PORTION OF SAID VERTICAL SLOT, SAID INCLINED SLOT BEING LOCATED ON ONLY ONE SIDE OF SAID VERTICAL SLOT, THE INTERMEDIATE AREA FORMED BY REMOVING THE MATERIAL BETWEEN THE SLOTS BELOW A FIRST HORIZONTAL PROJECTION-LINE EXTENDING FROM THE UPPERMOST CORNER OF SAID INCLINED SLOT DOWN TO A SECOND HORIZONTAL LINE EXTENDING BETWEEN ADJACENT SIDES OF SAID SLOTS, THE FIRST OF SAID TRANSVERSE SUPPORT MEMBERS HAVING A FIRST PROJECTION EXTENDING FROM ONE END THEREOF, SAID FIRST PROJECTION HAVING A NOTCH IN THE LOWER EDGE THEREOF, THE SECOND OF SAID TRANSVERSE SUPPORT MEMBERS HAVING A SECOND PROJECTION EXTENDING FROM ONE END THEREOF, SAID SECOND PROJECTION HAVING A NOTCH IN THE UPPER EDGE THEREOF, SAID FIRST PROJECTION EXTENDING INTO SAID VERTICAL SLOT FROM ONE DIRECTION WITH THE NOTCH THEREIN RECEIVING THE PART OF THE VERTICAL WEB OF THE LONGITUDINAL SUPPORT MEMBER IMMEDIATELY BELOW THE VERTICAL SLOT, SAID FIRST PROJEC-