AVer SA series - Manual (Page 268)

260
4. Secure the all hard disks on HDD rack (both side).
5. And then, put the HDD rack back into the DVR unit
and screw the HDD rack.
The connection interface
of hard disk should be this
direction inside the HDD
rack.
The round hole of HDD rack
must match the round bump at
chassis bottom of the DVR
unit.