Oki LD670 Mode D'emploi page 220

(3) Pass the roll paper under the guide roller. Lift the guide roller. Then,
with the printer top cover closed, insert the leading edge of the paper into
the rear of the printer.
Top cover
(closed)
Roll paper
Note : When the rolled paper is guided on top of the guide roller as illustrated in
Figure b shown below, the paper may not get through. Make sure that the
paper is guided under the guide roller as in Figure a shown above.
Note : If a paper roll is set as illustrated in Figure c shown below, its thermal
surface will be opposite and that nothing will be printed. Make sure to set a
paper roll as in Figure a shown above.
Guide roller
Guide roller
Fig.b
Fig.a
Guide roller
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Fig.c