Oki MC160n - Manual (Page 186)

186 Maintenance
5
Lift the machine and reinstall it on
top of Tray 2.
6
Open Tray 1 and reattach the dust cover.
7
If you removed the duplex option in step 1, reinstall it.
"
If the duplex option is not to be installed, install the locking pins.
While holding the grip of the locking pin vertical, insert the locking pin
into the opening on either the left or right side of the lower feeder unit
and, while pushing it in, turn it to either the left or the right. The locking
pin is installed when its grip is horizontal.
Installing the left and right locking pins secures the lower feeder unit to
the machine so it cannot be removed.