A torque-delivering cable is provided, which includes a first coupling. The torque-delivering cable and the first coupling are shaped so as to collectively define a first passage therethrough. A tissue anchor is further provided, which includes a tissue-engaging element and a second coupling, which second coupling is shaped so as to define a second passage therethrough. The first and the second couplings are interlockingly coupleable to each other. An elongate longitudinal locking element is additionally provided, which is shaped so as to define a sharp tip, and which (a) when reversibly disposed in the first and the second passages, maintains coupling together of the first and the second couplings, and (b) when withdrawn from the second passage, allows decoupling of the first and the second coupling from each another
