Canon Satera LBP5610 User Manual page 105

Align the circle mark on the lock release lever with that on the toner cartridge.
3
Remove the toner cartridge from the printer.
IMPORTANT
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If the toner cartridge cannot be removed, check if the circle mark on the lock
release lever is aligned with that on the toner cartridge. If you try to remove the
toner cartridge forcefully, this may result in damage to the printer.
Align at this part