Various fasteners are provided to hold together portions of mammalian tissue. The fasteners include fastening members with spaced-apart legs adapted to be passed through the tissue portions. One embodiment of the fastener has a mesh-like receiver around each leg for engaging the legs of another identical fastening member inserted from an opposite side of the tissue portions. In other embodiments, the receiver is a separate element and is applied to a side of the tissue portions opposite the fastening member to engage the legs of the fastening member. The receiver may have a variety of forms. A number of structures are disclosed for effecting engagement of the fastening member legs with the receiver.