I've had a Magnifax 4 enlarger about 25 years, using it only with the glassless 35mm or 6x6cm negative holders. I now need to use the pair of glass plates supplied with the enlarger for 6x9cm negatives, but in the absence of any instructions I'm at a loss in attempting to fit them. Whereas the metal neg. holders are cunningly held (wedged) in place, allowing the carrier to be opened and adjusted without the holder falling out, I can see no way of fixing the glass plates to the carrier. Is it possible that the (new) enlarger was supplied without some essential component, or can someone explain how the two glass plates are to be fitted? Any help gratefully received.