A surgical instrument includes an end effector having a clevis and first and second jaws mutually rotatable between open and closed positions. The jaws are proximally directed and laterally displaced relative to an axis of a control shaft of the instrument. The jaws hold first and second parts of a fastener, respectively. The first part includes a base having tissue-piercing posts, and the second part includes a second base defining apertures receiving the posts and a portion movable relative thereto between first and second orientations. When the posts are inserted into the apertures, the movable portion can be moved from the first unlocked orientation into the second configuration to lock the fastener parts together in an implanting position determined by various alignment measures, including markings or flags on the jaws or at the housing. The instrument is adapted to move the second part into the second configuration.