procedure TForm1.FormCreate(Sender: TObject);
begin
  ToolBar1.DockSite := true;
  ToolBar1.DragKind := dkDock;
  ToolBar1.DragMode := dmAutomatic;
end;

procedure TForm1.ControlBar1DockOver(Sender: TObject;
  Source: TDragDockObject; X, Y: Integer; State: TDragState;
  var Accept: Boolean);
begin
  Accept := (Source.Control is TToolBar);
  if Accept then
    with Source.DockRect do
    begin
      TopLeft := ControlBar1.ClientToScreen(ControlBar1.ClientRect.TopLeft);
      Right := Left + Source.Control.Width;
      Bottom := Top + Source.Control.Height;
    end;
end;