Canon BJC-4400 Series User Manual page 39

Insert the
single sheet.
After printing on thick paper or envelopes, set the paper thickness lever
(inside the printer) back to the left or center position before printing on
other paper types.
Chapter 3
Slide the paper into the manual feed slot in the back of
the printer.
Align the sheet with the left edge of the manual feed slot.
Hold the sheet for about two seconds until it feeds
automatically.
The printer will automatically load the paper into
position.
Paper Handling 3-13