Set ShapeTool property as SpRuleLine,then you can draw it by mouse.

Also,you can draw it by code.

Code example:

procedure TMainFrm.Button1Click(Sender: TObject); 
begin 
  if MyCAD1.GetShapeByName('RuleLineShape') = nil then 
    MyCAD1.AddShapeByCode(MyCAD1,spRuleLine, 'RuleLineShape', [MyPoint(131, 41), MyPoint(140,150)]); 
end;