Brother HL-3400CN - Manual (Page 165)

USER’S GUIDE
5-8
5. Install the new Oil Bottle into the Fusing Unit with the label facing
you. The Oil Bottle is keyed to prevent incorrect installation.
Fig. 5-7 Install the Oil Bottle
6. Lock the Oil Bottle Lock Levers securely.
7. Close the Top Cover.
8. Press the Power button to turn the printer On.