Methods, apparatus, and systems for occluding a multiplicity of parallel membranes, such as found in a patent foramen ovale (PFO). Methods, apparatus, and systems include the use of a positioning device that can be seated on the limbus of the septum secundum (SS). The positioning device includes a piercing member that can pierce the SS and septum primum (SP). The positioning device also includes a fastening member that can engage the SS and SP to fasten the tissues and thereby occlude a PFO.