It is important to develop a method of assembling a set of subpictures automatically into a mosaic picture, because a view through fiberscopes or microscopes with higher magnifying power is much larger than the field of view taken by a camera. This paper presents a method of assembling subpictures, where roughly estimated junctions called approximate junctions are employed for matching triangles formed by selected junctions in subpictures. To overcome the difficulties in processing speed and noise corruption, fuzzy rules are applied to obtain fuzzy values for the existence of approximate junctions and fuzzy similarity for congruent triangle matching. Some demonstration, exemplified by assembling microscopic metal crystal matrix photographs, are given to show feasibility of this method