A hinge is disclosed for a plastic film. This film has a predetermined thickness sufficient for the plastic film to remain planar in an absence of a first bending moment applied across the plastic film. The hinge includes at least one linear groove configured in the plastic film to reduce the predetermined thickness of the plastic film at the linear groove. The hinge permits preferential hinging of the plastic film at the linear groove responsive to a bending moment at the linear groove across the plastic film less than the first bending moment. The linear groove has insufficient depth to sever the plastic film and enables the hinge film to retain sufficient remaining thickness at the linear groove to permit hinging and not tearing of the plastic film at the linear groove. When the hinge is placed across a plastic film, and the film bent at the hinge, the film defines a first panel and a second panel with each panel disposed at an angle to one another at the hinge. This allows the first panel and the second panel to form a three dimensional structure to maintain the plastic film of each panel against bending. A square bottom bag design is disclosed where the hinge predisposes a plastic bag to open with a square bottom.