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First,drag the component of TRsRulerCorner and two TRsRulers to a form.

Then,set RsRuler1's Direction property as rdTop and HairLine property as True,RsRuler2's Direction property as rdLeft and HairLine property as True.

Last,Add code to realize when move mouse on a form then the ruler works.

Code example:

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X, 
  Y: Integer); 
begin 
  RsRuler1.HairLinePos:=X; 
  RsRuler2.HairLinePos:=Y; 
end; 

Note:you can use TPanel component to locate the position.