Extract a list of the specialist terms in the following text:
Little force is needed to operate the articulated arm. Hold the 
instrument at the fine adjustment F, use the other hand to 
slowly loosen the central handle A until the articulated arm 
can be moved. Guide the instrument to the desired position, 
then fasten the articulated arm in place by turning the central 
handle A. Adjust the instrument using the microfine 
adjustment F.
Be sure that
- the arm extension (distance from the fastening point to the 
measurement point) is as short as possible so as to 
improve measurement accuracy
- the fine adjustment screw F is facing downwards.
