Brother HL-L8260CDN Online User's Manual page 278

IMPORTANT
To avoid print quality problems, DO NOT touch the shaded parts shown in the illustrations.
5. Make sure the green lock lever (1) is in the release position, as shown in the illustration.
1
6. Gently slide the drum unit into the machine until it stops at the green lock lever.
7. Turn the green lock lever clockwise to the lock position.
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