fig1 - 3 illustrate the latch system 10 of the present invention installed on the loading nozzle 12 of a railroad car hatch . the top edge of the nozzle has a turned over flange or coaming 14 . one side of the nozzle mounts a hinge bracket 16 while the opposite side has a catch bracket 18 . it will be understood that the hinge bracket 16 will vary from one car manufacturer to the next . for example , present car builders in the united states include acf , trinity and pullman . they all make the hinge bracket differently . the catch brackets and catch bolts , however , are similar from one builder to the next . the catch bracket 18 has a catch bolt 20 pivotally connected thereto . the catch bolt itself has a shank 22 attached to a clevis 24 at one end . the other end of shank is pivotally connected to a locking clasp 26 by means of a pin 28 . the locking clasp has a pair of spaced side plates 30 joined by a top plate 32 which flares out into a widened handle portion 34 ( fig3 ). each side plate 30 has an open slot 36 on its lower edge and a hole 37 . operation of the catch bolt and locking clasp will be described below . the latch system 10 includes a central , elongated arm 38 . in a preferred embodiment the arm is a hollow member having a generally square cross section . for reference purposes only , the arm may be an aluminum extrusion about twenty - three inches long and about one inch square on the outside dimension , with a 0 . 125 &# 34 ; wall thickness . the ends of the arm 38 have attachment elements which allow the arm to receive the hinge and catch adaptors as will be explained more fully below . bolt holes near the ends of the arm comprise part of the attachment elements . the arm also has a central bolt hole 40 for mounting an unvented hatch cover . there is a drain opening 42 in the bottom of the arm to allow for drainage . c - shaped hatch cover brackets 44 may be bolted to the arm when a vented hatch cover is being used . bolts 46 extend through the holes in the ends of the arm for attaching both the cover brackets 44 and the hinge and catch adaptors . a vented hatch cover is shown at 48 in fig1 . details of the vented hatch cover are shown in u . s . pat . no . 5 , 064 , 089 . the brackets 44 surround the outer edges of the cover to attach the cover to the arm . pressure plates or wings 50 are attached to the bottom of the arm for use with a vented hatch cover . a hinge adaptor is shown generally at 52a . it has a plug that fits inside the end of the arm 38 and is retained by bolt 46 . a hinge pin 54 is pivotally mounted in the hinge bracket 16 and extends through an opening in the adaptor 52a . a catch adaptor 56 is attached to the opposite end of arm 38 . it has a plug similar to that of the hinge adaptor for retention by one of the bolts 46 . the outer end of the catch adaptor has a pair of prongs 58 which define a slot 60 between them . each prong carries a small peg 62 on it outside surface . there is a bore 64 ( fig5 ) through the central portion of the adaptor 56 . fig4 and 5 illustrate the latch system of the present invention mounting an unvented hatch cover 66 . the unvented cover has a pair of upstanding tabs 68 on its top surface which receive a mounting pin 70 for attaching the cover to the arm 38 . bolts 46 connect the hinge adaptor 52a and catch adaptor 56 to the ends of the arm . fig6 and 7 show the details of an alternate hinge adaptor 52b . the adaptor has a coupler portion 72b with a through hole 74 at the lower end for receipt of the hinge pin 54 . depressions 76b are located in the sides of the coupler portion for lightening the casting . an elbow 78b at the upper end of the coupler terminates at a connector in the form of a solid plug 80 . the plug has a square shape that fits snugly inside the hollow arm 38 . bore 84 accepts the retainer bolt 46 . fig8 and 9 show a further alternate hinge adaptor 52c which is essentially similar to adaptors 52a and 52b except the coupler portion 72c is somewhat shorter than coupler 72b and there is a boss 86 at the lower end . adaptor 52a has an even shorter coupler portion but is otherwise similar to adaptors 52b and 52c . the use , operation and function of the latch system are as follows . considering the vented hatch cover of fig1 - 3 , a user would first attach the wings 50 to the arm 38 . next the appropriate hinge adaptor 52 is inserted in one end of the arm and the catch adaptor 56 is inserted in the other end . then the brackets 44 are placed around the edges of the cover and the arm is laid over the cover and between the tabs of the brackets 44 . bolts 46 are inserted through the brackets 44 , arm 38 and plugs of the hinge and catch adaptors . to install the cover on a car , it is laid onto the hatch and the hinge pin 54 is placed through the hinge bracket 16 and the hole 74 . the hinge pin may be retained in any appropriate manner . to latch the cover , the bolt 20 is rotated about clevis 24 counterclockwise as seen in fig2 so the shank 22 resides in slot 60 of the catch adaptor 56 . the locking clasp 26 is rotated clockwise ( as seen in fig2 ) about pin 28 so that the slots 36 in side plates 30 receive the pegs 62 on the catch adaptor 56 . then the user pushes the handle 34 down toward the arm 38 until the handle lies flush against the arm as shown in fig2 . in this position the holes 37 in locking clasp 26 are aligned with the bore 64 in the catch adaptor 56 so that a cotter pin ( not shown ) or the like may be inserted to prevent inadvertent release of the locking clasp . changeover from the vented hatch cover 48 to an unvented cover 66 is done as follows . the locking clasp is released by reverting the steps just described . removal of hinge pin 54 then frees the arm 38 and cover 48 from the hatch nozzle . bolts 46 are removed to detach brackets 44 from the arm 38 . this releases the cover from the arm . wings 50 are also removed . if a different hinge adaptor is needed it can be inserted in the end of the arm . otherwise , the same hinge adaptor and catch adaptor are then re - inserted and fastened by bolts 46 . next the arm is placed between tabs 68 of the unvented hatch cover and the pin 70 is installed to connect the arm to the cover . with the cover placed on the hatch , hinge pin 54 is installed and locking clasp 20 is closed to complete the changeover . note that the same arm 38 and catch adaptor 56 are used for either type of cover . if the new cover is going on the same car , the same type of hinge adaptor is used . if the new cover is going on a different car , only the hinge adaptor need be changed , the other parts are used again . this system greatly reduces the amount of inventory that must be kept for different car and cover types . while a preferred form of the invention has been shown and described , it will be realized that alterations and modifications may be made thereto without departing from the scope of the following claims .