Pfaff 1245 Instruction Manual page 31

Fig. 9 - 01a
Turn the machine off!
Use only system 134 - 35 needles!
Loosen needle retaining screws .
Insert needles as far as it will go (the
longitudinal needle groove of the left-hand
needle must be pointing to the right and
that of the right-hand needle to the left).
Tighten needle retaining screws .
The selection of the correct
needle depends on the model of
the machine and the material and
threads being sewn.