procedure TMainForm.FormCreate(Sender: TObject);
const
  Colors: array[1..6] of TColor =
    (clWhite, clBlack, clBlue, clGreen, clRed, clYellow);
var
  I: Integer;
begin


  for I := Low(Colors) to High(Colors) do
    with TForm.CreateNew(Self) do
    begin
      Caption := 'Dock me in the main form';
      Color := Colors[I];
      DragKind := dkDock;
      DragMode := dmAutomatic;
      Position := poDefaultPosOnly;
      Width := 230;
      Height := 100;
      Visible := True;
    end;
end;