Epson AcuLaser C8600 Reference Manual page 42

5. Insert the stack into the cassette, as shown below. Make sure
that all the paper is under the metal retaining clip with the
printable surface down.
Note:
Loading the cassette with too much paper may cause paper jams.
6. Slide the back paper guide until it just touches the edge of the
stack of paper.
40 Paper Handling