An implant includes a central body and anchoring arms that extend proximally from the implant's downstream end portion and that are movable with respect to an upstream end portion of the implant. The implant is advanced into the heart using a catheter and is implanted at a native atrioventricular valve by positioning: (i) the anchoring arms in the ventricle, (ii) the central body between the native valve's leaflets, and (iii) a distal end of an elongate element into the ventricle. The elongate element is (1) pulled to apply a proximally-directed force to the anchoring arms to move the anchoring arms' distal ends axially with respect to the upstream end portion while the distal ends of the anchoring arms remain radially fixed with respect to a central longitudinal axis of the implant, and (2) removed from the subject's body. Other embodiments are also described.