This example uses three forms. The first form has its FormStyle property set to MDIForm. The other two have their FormStyle properties set to MDIChild and their Visible properties set to True. Add a main menu component and name one of the menu items TileForms. This is the code for the TileFormsClick handler. When you choose the TileForms command, the child forms tile vertically within the MDI frame form.
procedure TForm1.TileFormsClick(Sender: TObject); begin TileMode := tbVertical; Tile; end;