Canon Additional Finisher Tray-A1 Service Bulletin page 3

Slide Guid Stopper Installation Procedure
1) In the case of the Finisher-Q1/R1, open the front
door [1], remove the 3 screws [2], and detach the
front cover [3].
2) In the case of the Saddle Finisher-Q2/R2, open
the front cover [1].
3) In the case of the Finisher-Q1/R1, remove the 3
screws [1], and detach the rear cover [2].
4) In the case of the Saddle Finisher-Q2/R2, detach
the cable cover [1], remove the 6 screws [2], and
detach the rear cover [3].
5) Remove the 2 screws [1], and open the upper
cover of the finisher; then, detach the upper left
cover [3] as if to pull out the claw [2].