HP LaserJet 9040.9050 Multifunction Printer series - Manual (Page 101)

ENWW Multifunction finisher 97
4 Turn the small green knob at the top of the stapler unit clockwise until the staple cartridge
moves to the left of the stapler unit.
CAUTION The blue dot must appear in the window of the stapler unit before you remove the staple cartridge.
If you try to remove the staple cartridge before the blue dot appears in the window, you could
damage the finisher.
5 On the empty staple cartridge, squeeze the tabs together and pull the empty cartridge out.
6 Insert the new staple cartridge so that it locks into place.