I haven't used OD in awhile, but I believe there is a setting somewhere for reserve edge of screen. If it's checked, uncheck it.
That setting is under, settings, position.
To be clearer, right click on a dock, choose settings, pop up window to "set up docks"appears. should be on the HOME tab, leave it on that tab , down the list is position, click on that, find that Reserve edge setting.