Canon imagePRESS C1+ Reference Manual page 261

16
When you have finished aligning the rear edge retainer with the marks
for the desired paper size, fasten the rear edge retainer to the outer
size change plate with the blue screw using a coin or something
similar.
17
After you finish adjusting the outer size change plate, press [End].
18
Make sure that the inside lifter has lowered, and load the remaining
paper into the paper deck.
Adjusting the Machine
4
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