Apple LaserWriter 12/640 PS - Manual (Page 205)

Loading envelopes in the multipurpose tray
You can load a stack of 10 envelopes in the multipurpose tray for automatic
printing. You can also print envelopes manually by feeding them one
envelope at a time.
This illustration shows how to load a stack of envelopes in the
multipurpose tray.
Adjust the width guide on the multipurpose tray to the size of the envelope.
Hint: Direct the envelope to the face-up output to reduce curl.
If you print many envelopes: You can obtain an envelope cassette from
an Apple-authorized dealer that allows you to feed up to 50 envelopes
automatically.
WARNING Don’t use envelopes that have fasteners, snaps, or windows
when printing with the LaserWriter 12/640 PS printer. Also don’t use
envelopes that seal with peel-off strips or pressure-sensitive adhesives,
that are curled or wrinkled, or that are likely to discolor or melt at
temperatures of about 400° F (204° C). Printing on such materials can
damage the printer.
Slide the width guide
so that it rests against
the envelopes.
Stack the envelopes so that the tops
are to the right and the flaps are down.
205 Loading Paper