Apparatus and methods are provided, including a plurality of anchoring elements, each of the anchoring elements being an elongate element that is curved to define an opening. A housing holds each of the anchoring elements. A mandrel is reversibly disposable through the openings defined by the anchoring elements. The anchoring elements are configured such that, in response to removal of the mandrel from the openings, ends of the anchoring elements automatically move outwardly, and diameters of the openings decrease, due to elastic loading of the anchoring elements. Other embodiments are also described.
