Lexmark T420 User Reference page 58

The two values for Duplex Bind are:
Long Edge*
The asterisk (*)
indicates this is the
factory default
setting
Short Edge
Assumes binding along the long end of the page (left edge for portrait orientation
and top edge for landscape orientation). The following illustration shows long-edge
binding for portrait and landscape pages:
Binding
Back of
sheet
Portrait
Assumes binding along the short edge of the page (top edge for portrait orientation
and left edge for landscape orientation). The following illustration shows short-edge
binding for portrait and landscape pages:
Back of
sheet
Front of
next sheet
Portrait
Front of
next sheet
Binding
Binding
Binding
Back of
sheet
Landscape
58
Back of sheet
Front of next
sheet
Landscape
Front of
next sheet