To stack A0 (portrait) or A1 (landscape) paper properly, set up the output basket in A0 (portrait)/A1 (landscape) stack mode.
Make sure that the output basket is in basic mode.

Carefully pull out Bar 1 at an angle until it stops.

Bar 1
Bar 2
Bar 3
Lower Bar 1 so the basket is horizontal.

Lock the output basket in the horizontal position.

Slide Bar 3 toward the machine.

Bar 1
Bar 2
Bar 3

When you start printing, make sure that the output basket is open as shown above.