It looks as though the outlets to the boxes have some kind of cam friction device - the containers could contain some kind of ribbon (cloth?? metal??) (or wire???) and the ends come out of the slots, turn through 90 degrees (the edges appear rounded off) pass by the cam devices and thus wrap around what ever is under the device... the ends of the bars attached to the box lids will keep them from riding up in the slot... Still have no idea as to its actual use??? Serving wire ropes????