HI,
our radiators doesn´t have a specified In or OUT port. YOu have on e one side left and right ports, which can be used as IN and OUT. Depending on the radiator up to 3 on each side. ONe of them can be used as IN or OUT. THe other ones has to be closed. SOmetimes you have also a fill and Drain port on the other side. This port can´t be used as IN or OUT.