Brother HL-3450CN Service Manual page 364

iii) The table the printer is installed on is not level.
iv) The table surface the printer is installed on is not strong enough.
NOTE:
If you have a spirit level, put it on the output tray and install the printer as level as possible
referring to the level.
Spirit Level
Fig. A- 31
Fig. A- 32
Fig. A- 33
A-37
HL-3450CN SERVICE MANUAL
Level
1°
Level
1°