procedure TForm1.Button1Click(Sender: TObject);
const xoffset=300;
yoffset=200;
linespacing=10;
var i,xp,xn,yp,yn:integer;
begin
paintbox1.Canvas.Rectangle(0,0,paintbox1.width-1,paintbox1.height);
paintbox1.Canvas.MoveTo(xoffset,0);
paintbox1.canvas.LineTo(xoffset,paintbox1.height);
paintbox1.Canvas.MoveTo(0,yoffset);
paintbox1.canvas.LineTo(paintbox1.width,yoffset);
i:=1;
repeat
xp:=xoffset+i*LineSpacing;
xn:=xoffset-i*LineSpacing;
yp:=yoffset-i*LineSpacing;
yn:=yoffset+i*LineSpacing;
paintbox1.Canvas.MoveTo(xoffset-5,yp);
paintbox1.Canvas.LineTo(xoffset+5,yp);
paintbox1.Canvas.MoveTo(xoffset-5,yn);
paintbox1.Canvas.LineTo(xoffset+5,yn);
paintbox1.Canvas.MoveTo(xp,yoffset-5);
paintbox1.Canvas.LineTo(xp,yoffset+5);
paintbox1.Canvas.MoveTo(xn,yoffset-5);
paintbox1.Canvas.LineTo(xn,yoffset+5);
inc(i);
until not ((yp>0)
or (yn<Paintbox1.height)
or (xn>0)
or (xp<Paintbox1.width));
end;