A tissue anchor is provided that includes a head connected to a shaft, and a tissue-coupling element extending from the shaft. When the tissue anchor is unconstrained, the head is coaxial with an axis of the shaft, and the tissue-coupling element is generally orthogonal to the axis and is shaped such that if the tissue-coupling element were to be projected onto a plane that is perpendicular to the axis, (a) at least 80% of an area of a projection of the tissue-coupling element on the plane would fall within a first angle of 180 degrees in the plane having a vertex at the axis, and (b) the area would partially overlap, at least 3 mm from the vertex, both rays of a second angle of between 45 and 180 degrees in the plane having the vertex at the axis. Other embodiments are also described.