an improved foldable sheet plastic construction , employed in a butterfly pouch for use in making plastic laminated data cards , and in a plastic fan - fold product , both comprising adjacent panels made from a single sheet of plastic material that must be folded along a fold line into parallel facing relation . the fold line has a two - level hinge cut . a major portion of the fold line is cut to a predetermined depth that assures easy folding but may cause separation of adjacent panels ; a minor fractional portion of the fold line is cut to a substantially shallower depth to preclude separation of the panels on folding . in the preferred construction , the shallow cut is made at two or more spaced locations along the fold line to provide plural hinges .