An overtube apparatus for insertion into a body is described herein. The assembly includes an overtube having a lumen defined throughout. The distal end of the overtube member has two or more windows in apposition configured to draw in tissue via a vacuum. A drive tube, which also defines a lumen, is inserted and is freely adjustable within the overtube. A spiral or helical fastener, which is temporarily attached to the drive tube distal end, is positioned within the overtube lumen. Endoscopic devices can be inserted within the drive tube lumen and advanced past the distal ends of both the drive tube and overtube. A pump provides the vacuum to draw apposed regions of tissue from within a hollow body organ into the windows of the overtube. Once the tissue has been invaginated, the drive tube is rotated to advance the fastener into the tissue to fasten them together.