Passenger rear door sticking / rubbing

Hi

Bought my freelander last week and have noticed the passenger rear door is pretty hard to open and close. It seems to be the flat hinge part in the middle of the door which moves in and out of itself. It seems to be sticking quite bad, ive tried oil etc but still no joy . Does anyone know what this part is actually called and if it can be replaced.

Cheers

It is there to slow the door movement down when opening/closing it. Also prevents the door opening to far and hitting the center pillar. One of mine was very stiff so I squirted penetrating oil where it slides in and after a week or so it eased off. I couldn't see any easy way of taking it out to service it.