Bulkhead hold down

Claim 1

IN A SYSTEM FOR SUPPORTING A DOOER OR THE LIKE FOR MOVEMENT ALONG SPACED PARALLEL SIDE WALLS; TRACK ASSEMBLIES ADAPTED TO BE MOUNTED ON SUPPORT STRUCTURE ADJACENT SAID DOOR ALONG EACH SIDE WALL, EACH OF SAID TRACK ASSEMBLIES COMPRISING A TRACK MEANS HAVING A SUPPORT SURFACE FOR RECEIVING A WHEEL ASSEMBLY AND A GUIDE GROOVE SURFACE SPACED THEREFROM; WHEEL ASSEMBLIES ON EACH SIDE OF THE DOOR ADJACENT THE SIDE WALLS, EACH COMPRISING A GUIDE WHEEL MEANS HAVING A FIRST PERIPHERAL DIAMETER AND A SUPPORT WHEEL MEANS HAVING A SECOND PERIPHERAL DIEMETER VARYING FROM THE PERIPHERAL DIAMETER OF SAID GUIDE WHEEL MEANS, SAID SUPPORT SURFACE OF SAID TRACK MEANS BEING ADAPTED TO RECEIVE AND SUPPORT SAID GUIDE WHEEL MEANSE AND SAID SUPPORT WHEEL MEANS, SAID GUIDE WHEEL MEANS AND SAID SUPPORT WHEEL MEANS BEING MOUNTED ON AND SUPPORTED BY AID SUPPORT SURFACE OF SAID TRACK MEANS; AND RESTRAINING MEANS MOUNTED ON AND OVERLYING AND SUPPORTED BY SAID WHEEL ASSEMBLIES AND EXTENDING TOWARD SAID GUIDE GROOVE SURFACE, A PORTION OF SAID RESTRAINING MEANS BEING LOCATED CLOSELY ADJACENT SAID GUIDE GROOVE AND PREVENTING ACCIDENTAL OR INADVERTENT DISPLACEMENT OF SAID WHEEL ASSEMBLIES.