A first element (91) includes a first arm (92) and a second arm coupled thereto and having a concavity (103) facing the first arm and defining a space (96). In an open state, a tissue anchor portion (46) moves into the space through a gap between distal portions (94) of the first and second arms. In the closed state, the anchor portion is not movable through the gap. A second element (82) is movable with respect to the first element, such that, while the portion (46) of the anchor (40) is within the space, and the first element is in the closed state, in a first position of the second element, the portion of the anchor is movable within the space, and in a second position of the second element, the second element applies torque to the anchor by rotating the second element. Other embodiments are also described.