A leaflet support for use with a native valve of a heart of a subject includes a frame that defines an array of adjoining cells, as well as an aperture between an upstream side and a downstream side of the frame. When placed against an annulus of the heart, the frame facilitates blood flow, via the cells, between the upstream side and the downstream side. The leaflet support further includes a barrier that is impermeable to blood flow, and that is coupled to the frame in a manner that obstructs blood flow through the aperture. The leaflet support further includes ventricular legs, that each extend radially outward and upstream, toward the frame. Other embodiments are also described.