The field flattener is accessed via the plateholder recess. The plateholder or dummy should be removed to expose the two M6 Allen screws located close to the outer surface of the field flattener element. Remove the screws whilst keeping a careful hold of the flattener cell. Movement of the plateholder slide may enable better hold of the cell to be established. When withdrawing the unit be careful to avoid fouling of the 45 degree mirror surface on the surrounding case plate. Replacement should be obvious.