Replace the position (1~4 holes) used by the aperture and record the position of the aperture after replacement. After replacing the hole need to make accessories︰items 4.2 and 4.3 in the procedure of replacing the aperture by SEM (S-8820) machine (if the position of the 4th hole has been changed before replacement need to replace the aperture,as in step 4.3.3.8).