Canon BJ-W9000 Service Manual page 437

Part 3: Operations
7. While lifting the take-up unit a little, push the take-up unit to the rear until it stops.
At that time, make sure that the hook of the holder plate engages the take-up unit.
Hook of the holder plate (right)
8. Slide the take-up unit to the left end.
CAUTION
Unless the hook of the holder plate engages the take-up unit correctly,
you cannot slide the take-up unit to the left.
Figure 3-8
Figure 3-9
3-6
TU-01
Hook of the holder