Xerox 3400N - Phaser B/W Laser Printer Service Manual page 21

Always place the printer on a flat, stable surface.
I
Maintain the clearance distances below for ventilation purposes on all sides.
I
Do not obstruct the cables, paper trays or output trays.
I
10 Xerox Phaser 3400 Printer Service Guide
6 in
15 cm
12 in
30 cm
6 in
15 cm
P3400-007