This 3-part kit consists of 2x rack-mount 'ears', 1x blank plate and all fastening hardware. To mount 2 4081's into a 19"rack enclosure, fasten the 2 units together, then use the 2 rack-mount 'Ears' - one on either side.
To mount one unit, fasten an 'ear' to one side of the unit and the blank plate to the other side of the unit.