Compressor

Hi All,

Hope someone can help, not mechanically minded so will try to explain best i can so here goes.

I am trying to replace compressor on series 2 disco followed the guide as writted by a member everything was going great untill I got to the two brass bolts onto the valve block one tighted nicely the other wont tighted just keeps going around therefore all the air is escaping, I belive this part is called an olive ring.
If anyone could guide me as to what to do next I would be grateful
Thanks in advance, I do hope I have explained myself ok

All ok now, cut one of the pipes and replaced a new screw and olive clip, it seems that the previous owner had put on two olive clips on one pipe hence the not tightening problem.
And up she went...............