Yashica ML 28-85mm Reassembly   Reverse the tear-down process, using a new/clean Pec-Pad to support the optical block as it's raised and inserted into the upside-down barrel, before flipping the lens over to an upright position. Using the spanner, tighten the block to be a snug fit, then clean the inner threads with 99% alcohol to clear grime and debris before replacing the face ring.