Need tutorial on GtkHandleBox

[George Brink <siberianowl yahoo com>]

I am trying to do a dockable widget.
I know it can be done with GtkHandleBox.
Cannot define where my widget can be docked in main window.

Now I have:

    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    hbox = gtk_hbox_new(FALSE, 0);
    gtk_container_add(GTK_CONTAINER(window), hbox);

    handlebox = gtk_handle_box_new();
    gtk_handle_box_set_handle_position(handlebox, GTK_POS_TOP);
    gtk_box_pack_start(GTK_BOX(hbox), handlebox, FALSE, TRUE, 0);

This allows my widget to be docked only on the left side of main window. 
How to dock to the right/top/bottom sides? What should I use instead of 
GtkHBox for the initial widget placement?
Also, I do not see callbacks in GtkHandleBox to catch the docking to a 
different sides of the window (in order to switch the orientation of 
widgets inside my handlebox).