Axiel Ball joint I think it is called, as said stilsons or plumbers grips if they have had aftermarket ones (copies) fitted they come with flats, genuine Renault don't, as they have as usual a special tool to remove them, I found the stilsons better myself, lock steering right over to get to it, they can be quite tight to start this is becasue they are thread locked on, once you move it is will come off ok, make sure he puts the plastic orange washer back on the right way around (mark it) behind the ball joint this is a bump stop for the rack, also he MUST use thread lock when he winds the joint back on to the rack, I replaced the track rod end as well as you have to remove it to get the boot off and they are not that dear off ebay.
If it is REALLY tight, he may have to use some grips to stop the steering rack arm twisting as this "can" happen, mine where ok once you "broke" the thread lock seal, so remember.
1 - what out for orange thrust washer, must be put back the right way so mark it.
2 - USE thread lock when winding on new joint otherwise they can wind off again (not a good idea for steering) that hardest job on mine was actually undoing the track control locking nut they where rusted together.:crazy: