flexible member 20 from retreating from this position fig5 b illustrates a locking mechanism without leaf springs that can be used where arcuate shaped flexible member 20 remains in the closed position by virtue of its own resiliency the locking mechanisms shown in fig5 a and 5b are of course offered by way of example as other schemes of retaining closure device 12 in a desired position may be devised fig6 illustrates an alternative embodiment of the invention in which a hinge plate 81 is comprised of two hinge leafs 82 and 84 held to a structure not shown by conventional fasteners 86 hinge leafs 82 and 84 each have a series of axially aligned tubular knuckles 88 and 90 respectively knuckles 88 of hinge leaf 82 are joined with knuckles 92 of flexible member 20 by a pin 94 with knuckles 90 of hinge leaf 84 being joined with knuckles 96 of support frame 44 by a pin 98 the two hinge leaf embodiment of hinge plate 81 may be utilized with a flexible member having knuckles formed directly in its ends as does flexible member 20 of fig3 or may be used with a flexible member having hinge leafs attached at its ends such as flexible member 20 in fig6 shown with a hinge leaf 100 being attached by fasteners 102 at one end thereof a divided hinge plate such as that shown in fig6 could be useful for a number of reasons such as component availability ease of manufacturing ease of installation and for adjustment reasons where fine tuning of the position of closure device 12 is considered desirable although those skilled in the art will realize that a variety of applications and embodiments of the invention are possible.