Canon MF6180dw Manual page 223

3. Close the lower rear cover.
2
Place a document in the feeder.
"Placing Documents"
"Supported Document Types"
3
Press [ ].
4
Press [ ] (2-Sided).
You can display the setting screen also by selecting <2-Sided> in the copy mode screen.
5
Select <2->2-Sided> with [
If you want to specify how to open original or copy
(1) Select <Format Settings> with [
] or [ ] and press [OK].
] or [ ] and press [OK].