When the Navigator is set in Relative Mode, the far right edge of the touchpad can be used to scroll vertically within application windows and the bottom edge can be used to scroll horizontally. (note: horizontal scrolling is only available on Windows Vista, 7 and Mac OS X)

In order to access the scroll zone functionality the finger/thumb you must first lift your finger/thumb off of the touchpad surface and back down in that zone. Once in the zone, you can slide finger/thumb up or down or left or right.