Canon Satera LBP7700C User Manual page 73

 Slide the rear paper guide.
72
(1) Hold the lock release lever.
(2) Slide the paper guide to be aligned with the loaded paper.
(1)
IMPORTANT
Be sure to align the paper guides with the paper.
If the paper guides are too loose or too tight, this may result in misfeeds or paper
jams.
(2)