Canon PC800 Series Service Handbook page 18

CHAPTER 2 STANDARDS AND ADJUSTMENTS
4) Turn the cable drive pulley [3] so that the three shafts [2] of the mirror positioning tool for the front
and the rear may be arranged as shown.
2-4
[2]
Figure 2-7 (rear)
[2]
Figure 2-8 (front)
[3]
[2]
[2]