Identify a locking part on upvc french patio door Post questions and find answers on glazing, double glazing, upvc glazing, conservatory glazing, fixtures and fittings etc....

[foldy]

Hi , Can anyone tell me want this is call?
This one is ok , but the lower one is damaged, the larger silver coloured screw that adjusts the “C” shape jaw that the roller locks into been broken so no adjustment can be made.
Thanks