Plaster frame

Claim 1

IN A PLASTER FRAME, THE COMBINATION OF: A PAIR OF RAILS, THE UPPER AND THE LOWER LONGITUDINAL EDGES OF EACH RAIL BEING SHAPED TO DEFINE A REVERSE BEND, SAID UPPER REVERSE BEND OF EACH RAIL BEING PROVIDED WITH AT LEAST ONE PAIR OF VERTICALLY ALIGNED SLOTS, AND SAID LOWER REVERSE BEND OF EACH RAIL HAVING A VERTICALLY DISPOSED TAB STRUCK FROM THE UPPER LATERAL SURFACE THEREOF AND THEREBY PROVIDING A SLOT IN SAID UPPER SURFACE OF SAID LOWER REVERSE BEND, SAID SLOT BEING IN VERTICAL REGISTER WITH SAID PAIR OF VERTICALLY ALIGNED SLOTS IN SAID UPPER REVERSE BEND; A JOINING PLATE OVERLYING AND NESTING WITH THE ADJACENT ENDS OF SAID RAILS, THE UPPER LONGITUDINAL EDGE OF SAID JOINING PLATE BEING PROVIDED WITH A REVERSE BEND WHICH NESTS WITH THE REVERSE BEND WHICH CHARACTERIZES THE UPPER LONGITUDINAL EDGE OF EACH OF SAID RAILS, SAID REVERSE BEND OF SAID JOINING PLATE HAVING A PAIR OF VERTICALLY ALIGNED SLOTS FORMED THEREIN NEAR EACH END THEREOF AND IN REGISTER WITH THE CORRESPONDING VERTICALLY ALIGNED SLOTS FORMED IN THE UPPER LONGITUDINAL EDGE OF SAID RAILS, AND THE LOWER LONGITUDINAL EDGE OF SAID JOINING PLATE BEING A LATERALLY EXTENDING FLANGE OVERLYING THE UPPER LATERAL SURFACE OF THE LOWER REVERSE BEND OF SAID RAILS AND TERMINATING FLUSH WITH THE VERTICAL SURFACE THEREOF, SAID LATERALLY EXENDING FLANGE OF SAID JOINING PLATE BEING PROVIDED WITH CUTOUTS IN REGISTER AND CO-EXTENSIVE WITH THE SLOTS IN THE UPPER LATERAL SURFACE OF THE LOWER REVESRE BEND OF SAID RAILS WHEREBY AN INTERLOCKING OF THE LATERALLY EXTENDING FLANGE OF THE JOINING PLATE WITH THE VERTICALLY DISPOSED TABS STRUCK FROM THE UPPER LATERAL SURFACE OF THE LOWER REVERSE BENDS OF THE RAILS IS EFFECTED; AND A PIN EXTENDING THROUGH EACH SERIES OF VERTICALLY ALIGNED SLOTS AND CUTOUTS WHEREBY SAID RAILS AND SAID JOINING PLATE ARE SECURELY FASTENED TO ONE ANOTHER.