same position relative to the glass flats and carriage assembly 24 each time a third magnetic means 68 is cemented or secured by other known means to the bottom of the fiche carriage 24 this is similar to the first magnetic means 60 in that one or two magnetic poles are sufficient a fourth magnetic means 70 is secured to the top of the base structure 14 the fourth magnetic means 70 is similar to the second magnetic means 62 in that it is composed of a series of magnets having alternate magnetic poles adjacent each other thus the firmly attached fourth magnetic means 70 provides fixed polar reference points for the third magnetic means as it slides in the x direction across the base structure 14 as seen in fig5 there are seven positions where the third magnetic means 68 will have the greatest magnetic attraction for the poles of the fourth magnetic means 70 the magnetically held or latched positions of the fiche carriage 24 will be useful only if the images on the fiche 38 are accurately positioned the fiche must be made with accurate image placement in both the x and y directions the placement of the images must also be uniform from fiche to fiche so that the image will be properly positioned in the image projection system when the carriage assembly 24 is in one of its magnetically held positions.