Draw lines over a TStringGrid

Problem/Question/Abstract:

I have a TStringGrid with objects put in big coloumns of 4 normal columns. How can I draw a black line from top to bottom over the gray line that the grid itself draws?

Answer:

Handle the OnDrawCell event for the grid. If the cell you are asked to draw is in the column in question you draw the part of the line that crosses the cell:

procedure TForm1.StringGrid1DrawCell(Sender: TObject; ACol, ARow: Integer;
  Rect: TRect; State: TGridDrawState);
begin
  if (aCol = 1) and not (gdFixed in State) then
  begin
    with (sender as tstringgrid).canvas do
    begin
      Pen.Color := clBlack;
      Pen.Width := 2;
      Pen.Style := psSolid;
      MoveTo(rect.right - 1, rect.top);
      Lineto(rect.right - 1, rect.bottom);
    end;
  end;
end;