A system is transluminally advanced into the heart of a subject. A first portion of the system is positioned through a native valve of the heart, the system including wires disposed at the first portion. The first portion is stabilized at the native valve by positioning a distal portion of the system within a blood vessel of the subject. While the distal portion of the system remains within the blood vessel, the wires are induced to bow laterally such that the wires press against the native valve. While the wires remain pressed against the native valve, the shape of the wires is radiographically imaged. An anchor is transluminally anchored to tissue of the native valve, facilitated by the imaging. Other embodiments are also described.