Oki C8800 User Manual page 22

> For two-sided (duplex) printing on headed paper load
the paper with pre-printed side down and top edge
away from the printer. (Optional duplex unit must be
installed for this function.)
> Envelopes should be loaded face up with top edge to
the left and short edge into the printer. Do not select
duplex printing on envelopes.
> Do not exceed the paper capacity of about 100 sheets
or 10 envelopes. Maximum stacking depth is 10mm.
5. Press the tray latch button (5) inwards to release the
paper platform, so that the paper is lifted and gripped in
place.
Set the correct paper size for the multi purpose tray in the Media
Menu (see "Menu Functions").
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