GNOME: ( /usr/libexec/gnome-panel-add ) returns ( right_panel is not an existing panel identifier )

GNOME: ( /usr/libexec/gnome-panel-add ) returns ( right_panel is not an
existing panel identifier )

This works fine:
/usr/libexec/gnome-panel-add
--launcher="/usr/share/applications/gedit.desktop" --panel="top_panel"
--right-stick
so I changed top_panel to right_panel, but it did not work.
How can I identify the panel that is on the right side?
I have 2 panels, one on top and one on the right side.