The rack mounts for the OE-MD may look different than your standard rack mounts, however they effectively work the same.
To mount your rack mounts on the OE-MD, you will want to make sure the thinner part of the rack mount connects to the side of the recorder. This allows it to fit between the ventilation holes on the sides of the recorder.
From here, line up the holes on the mount with the screw holes on the recorder, and use the included screws to mount the rack mount to the recorder. Once both brackets are mounted, they should be wide enough to allow you to mount the recorder into your server rack.