Oce 3121 Technical & Service Manual page 554

Fit the tension tool to the arm of the tension shaft: at the front.
11
Do not touch the outer surface of the fusing film, or the surface of
Warning:
the heater.
Fusing film
Rubber ring
If you do not have the pressure tools, push the arrowed point and remove
Note:
the fusing film.
414 TSM Océ 3121 Dis-/assembly