Hoang, I'm just presenting an option, not a recommendation. Different folks like to do the 4th side different ways. If your milling square stock, using the planer for the 4th side is very intuitive, and should give a very accurate, repeatable dimension and a great surface. As one moves away from square, at some point (w/h ratio) people will move to the TS. That point will vary between the user and the equipment they are using.