Canon LBP7780CX User Manual page 164

4
Adjust the paper guides to the stack of paper so as to leave no space in between.
IMPORTANT
Be sure to adjust the paper guides to the stack of paper so as to leave no space in between.
If the paper guides are too loose or too tight, this may result in paper being misfed or paper jams.
5
Hold down the paper, then set it under the hooks (A) on the paper guides.
Make sure that the paper stack does not exceed the load limit mark lines (B).
Be sure that the paper stack does not exceed the load limit mark lines. If the paper stack exceeds the load limit mark
lines, this may result in paper being misfed.
6
Set the paper drawer in the printer.
Next, register the paper size
"Registering the Paper Size and Type"