in fig1 an embodiment of a ball mat is viewed in perspective diagonally from above . the ball mat comprises a cover plate 11 and , parallel thereto , a floor plate 12 ( cf . fig2 ). at its sides the ball mat is bounded by side profiles 19 , 20 , 21 , 22 . the side profiles 19 , 20 , 21 , 22 are joined to one another by corresponding outer corner pieces 53 , 54 , 55 and 56 , which can be inserted into the side profiles . by the use of this technique , with appropriate modification of cover plate 11 and floor plate 12 there are almost infinitely many possible configurations of the ball - mat contours and openings ( building - block system ). the cover plate 11 , floor plate 12 and side profiles 19 - 22 between them define an interior 16 . by way of apertures 18 in the cover plate 11 a plurality of holders 13 for ball elements 15 ( cf . fig2 ) is inserted into the interior 16 . corresponding ball elements are described in detail , for example , in the german patent de 38 05 494 . the remaining space in the interior 16 , in the embodiment shown here , is filled with foam , so that in the interior 16 of the ball mat a foamed body 17 is formed . the foamed body 17 stiffens the ball mat , attenuates vibrations and prevents moisture or liquids from spreading out within the interior 16 . in principle the interior 16 between cover plate 11 and floor plate 12 can also be filled with other material ( e . g ., balsa wood , special aluminum honeycomb cores or the like ). the ball mat shown in fig1 further comprises three troughs 38 , 39 , 40 , which are provided for the installation of drive units 50 . in addition , the ball mat comprises a plurality of openings 30 that allow latches 35 to be inserted . the latches 35 are provided to hold the cargo in place on the ball mat . the structure of the ball mat shown in fig1 can be still better understood by examining the view in fig2 a section along the line ii -- ii in fig1 . between the cover plate 11 and the floor plate 12 the previously mentioned holders 13 for the ball elements 15 are seated ; they have a substantially pot - like cylindrical shape . the positions of the holders 13 correspond to those of the apertures 18 in the cover plate 11 . at their ends towards the underside of the cover plate 11 the holders 13 comprise devices 37 to act as gaskets , in order to create a -- preferably watertight , at least for splashes -- seal between cover plate 11 and holder 13 . the sealing devices 37 are here constructed as a collar around the upper edge of the holder 13 , such that the collar makes contact over a broad area with the lower surface of the cover plate 11 . the holder 13 for the ball element 15 , which is indicated only schematically in fig2 stands on the floor plate 12 by way of devices including an annular projection 29 or a circumferential collar . upward out of the ball element 15 there projects an upper segment of a rotatably mounted ball 14 . in the floor plate 12 a bore 41 concentric to the holder 13 is provided , through which any liquid that enters the ball element 15 can flow out . the ball element 15 comprises in its lower region a corresponding bore , which permits liquid that has entered to drain away . because the holder 13 is disposed between cover plate 11 and floor plate 12 as described , loads imposed vertically on the ball mat are transmitted to the holder 13 and uniformly transferred into the ball mat , in particular onto the floor plate 12 . the ball mat is interrupted by an opening 30 visible in the sectional view shown here . the opening 30 is bounded by side profiles 31 , 32 , 33 , and 34 ( cf . fig1 ), which close the ball mat in a splashproof manner and stiffen it in the corresponding edge region the opening 30 is closed off at the bottom by a fixation plate 42 , which over a region at the lower edges of the side profiles 31 , 32 , 33 and 34 is connected to the side profiles 31 , . . . , 34 , for example by blind rivets . on the fixation plate 42 a previously mentioned latch 35 is disposed . the latch 35 serves to hold cargo in place on the ball mat . at the same time the ball mat is fixed to the floor of the aircraft by way of the latch 35 , by means of a bolt 43 connected to the latch 35 . the ball mat is thus fixed to the floor of the aircraft by way of the fixation plate 42 ( and the latch 35 ). as a result of this relatively indirect attachment , transverse forces and vibrations , parallel to the cover plate , are attenuated before being transferred to the aircraft floor , which is relatively sensitive to such stresses . sideways forces exerted directly on the latch 35 are also attenuated by the fixation plate 42 , which thus also has a stabilizing action on the latch 35 . the side profiles 19 , 20 , 21 and 22 on their surfaces facing the inside of the opening comprise a groove that runs around the entire opening and is provided so that a lid , not shown here , can be set into the opening and locked in place . with such a lid , openings 30 can be closed off when not needed . the structure of the side profile 22 bounding the outer edge of the ball mat corresponds to that of the side profiles 31 , 32 , 33 and 34 bounding the opening 30 . details are shown in fig3 . in fig3 the left part of the sectional view in fig2 is enlarged . the side profile 22 has an upper side 27 and a lower side 28 , such that the side profile 22 closes off the edge of the ball mat with its upper side 27 flush with the cover plate 11 and its lower side 28 flush with the floor plate 12 . on its side towards the ball mat the side profile 22 is provided with planar bearing surfaces 23 , 24 on its upper side 27 and lower side 28 , respectively . as a result , the cover plate 11 and the floor plate 12 rest on the bearing surfaces 23 , 24 of the side profile 22 in such a way that part of the side profile 22 extends into the mat , between cover plate 11 and floor plate 12 . the planar bearing surfaces 23 , 24 , which extend in the long direction of the side profile 22 , respectively come into contact with the inner surfaces 25 , 26 of cover plate 11 and floor plate 12 , thus forming a splashproof seal . in addition , the ball mat is strengthened at its edges by side profiles arranged in this way . in fig4 the ball mat of fig1 is shown in perspective , as viewed diagonally from below . the floor plate 12 can be seen , in which bores 41 are provided in positions corresponding to those of the holders 13 for the ball elements 15 . the bores 41 allow liquids that may enter the ball elements or holders to drain away . furthermore , in fig4 the undersides 44 , 45 , 46 of the troughs 38 , 39 , 40 are visible . in the undersides 44 , 45 , 46 of the troughs 38 , 39 , 40 holes have been made through which cables can pass to the associated drive units . fig5 shows part of the ball mat in a sectional view along the line v -- v in fig1 such that the plane of section passes through a trough 38 for a drive unit 50 , which is also shown in fig5 . the trough 38 for the drive unit 50 is -- as can be seen in fig5 -- constructed in one piece , such that side profiles 51 , 52 of the trough are inserted completely between the cover plate 11 and the floor plate 12 . in fig6 a modified embodiment of a ball mat is shown in perspective from above . for clarity , components the same as or corresponding to those of the ball mat according to fig1 to 5 are identified by the same reference numerals . the ball mat is shown fully assembled in fig6 . in this embodiment the space in the interior 16 is not filled with foam but rather packed with a solid body ( e . g ., of balsa wood ). so that the entry of liquids can be reliably prevented , here all parts are attached to one another by adhesive or by way of a sealing device . the cover plate 11 can be painted with non - slip varnish to provide a secure footing . in fig7 the ball mat according to fig6 is shown in exploded view . this drawing reveals how the ball mat in this embodiment is assembled . in addition , it clarifies how the ball - mat contours and edge cut - outs can be varied in a simple manner , as circumstances require . at the top is the cover plate 11 , which here consists of a metal sheet 1 . 5 mm thick . the shape of the cover plate 11 can be produced by laser cutting or stamping . the holders 13 and the side profiles 19 , 20 , 21 and 22 and 31 , 32 , 33 and 34 are riveted or glued to the cover plate . below the cover plate 11 the holders 13 are shown . below these is the packing body 17 , which in this embodiment is made of balsa wood . the side profiles 19 , 20 , 21 , 22 and 31 , 32 , 33 and 34 shown below this are arranged to correspond to the outer contour of the cover plate 11 and floor plate 12 by connecting them with outside corner pieces 53 , 54 , 55 and 56 or inside corner pieces 57 , 58 , 59 and 60 ( building - block system ). at the bottom in fig7 various fixation plates 42 , 42 &# 39 ; can be seen . these are riveted to the floor plate 12 and serve both to fix the ball mat to the floor of the aircraft and to provide a surface for mounting latches , drive units or the like . in fig8 a sectional view along the line viii -- viii in fig6 is shown . fig9 shows an enlarged view of a side profile 20 , into which an outside corner piece 53 can be inserted . an inside corner piece 57 is also shown enlarged . it is evident from fig9 that with side profiles 19 , 20 , 21 and 22 and side profiles 31 , 32 , 33 and 34 plus the outside corner pieces 53 , . . . , 56 and inside corner pieces 57 , 58 , 59 and 60 nearly any desired contour of a ball mat can be created .