HP LaserJet 9050 Printer series - Manual (Page 63)

ENWW Using the optional stacker/stapler 61
Loading staples
Load staples using this procedure.
To load staples
1 Move the stacker/stapler away from the printer.
2 Open the stacker/stapler-unit door.
3 Lift up on the green tab on the empty staple cartridge and pull it out.