While it's very dark under the car, you can see the latches on the side of the hopper  at the outer edge of the door, apparently Wine door latches. Two latches, one on either side of the car, secure a pair of doors which are connected with (typically) a steel angle or channel.

This photo seems to indicate that the hoppers were not joined:

Yes indeed. This car has individually latched doors, with what appear to be Enterprise unit latches. The latch is more or less at the center of the door.  .