Sliding closure construction

Claim 1

A SLIDING DOOR ASSEMBLY ADAPTED FOR INSTALLATION IN AN OUTER WALL OF A STRUCTURE AND COMPRISING A FRAME FORMING AN OPENING AND INCLUDING A HEAD MEMBER AND A SILL MEMBER INTERCONNECTED BY SPACED VERTICAL STILES; TRACK MEANS PROVIDED IN SAID SILL MEMBER; A HIGH UPWARDLY EXTENDING FIN AND AN OUTWARDLY SPACED SHORT RIB, SAID FIN AND SAID RIB BEING FORMED INTEGRALLY WITH AND LONGITUDINALLY OF SAID SILL MEMBER AND POSITIONED INWARDLY OF SAID TRACK MEANS; A FIXED DOOR IN SAID OPENING ADJACENT ONE OF SAID STILES HAVING ITS LOWER END POSITIONED AGAINST THE OUTER SURFACE OF SAID FIN; A GENERALLY U-SHAPED INVERTED THRESHOLD BETWEEN SAID FIXED DOOR AND THE OTHER OF SAID STILES HAVING A FIRST LEG POSITIONED AGAINST THE OUTER SURFACE OF SAID FIN AND HAVING A SECOND LEG TERMINATING IN A GROOVE, SAID RIB BEING RECEIVED IN SAID GROOVE, AN UPPER BIGHT PORTION OF SAID THRESHOLD INTERCONNECTING SAID LEGS AND FORMING TREAD MEANS, SAID TREAD MEANS EXTENDING OUTWARDLY BEYOND SAID SECOND LEG; GROOVE MEANS FORMED ADJACENT THE OUTER EDGE OF SAID TREADS MEANS FOR CARRYING WEATHERSTRIP MEANS; A MOVABLE DOOR POSITIONED IN SAID OPENING ON SAID TRACK MEANS FOR SLIDING MOVEMENT EXTERIORLY OF SAID FIXED DOOR BETWEEN AN OPEN AND CLOSED POSITION; WEATHERSTRIP MEANS IN SAID GROOVE MEANS SEALINGLY ENGAGABLE WITH THE LOWER INNER SURFACE OF SAID LAST MENTIONED DOOR WHEN SAID DOOR IS IN A CLOSED POSITION; SAID OUTER WALL, THE OUTER PORTION OF SAID TREAD MEANS, AND THE LOWER INNER SURFACE OF SAID LAST MENTIONED DOOR DEFINING A CHAMBER ABOVE SAID SILL MEMBER EFFECTIVE TO PREVENT SUCTION OF WATER PAST SAID WEATHERSTRIP MEANS; AND SEALING MEANS BETWEEN SAID FIN AND SAID FIRST LEG.