A system for use at a heart of a subject, the system comprising an annuloplasty structure that comprises: a flexible sleeve having a proximal sleeve-end, a distal sleeve-end, and a circumferential wall that defines a longitudinal lumen between the proximal and distal sleeve-ends; an elongate contraction member having a proximal end and a distal end, wherein the proximal end of the contraction member is attached to the sleeve at an attachment point of the sleeve, the attachment point and the proximal sleeve-end defining a proximal sleeve-end-portion, and a proximal end portion of the contraction member extends, in association with the circumferential wall of the sleeve, from the attachment point toward the distal sleeve-end and enters the lumen of the sleeve at an entry point of the sleeve so that a distal end portion of the contraction member is disposed within the lumen, the entry point and the distal end of the sleeve defining a distal sleeve-end-portion; and a plurality of tissue anchors configured to extend through the circumferential wall and into tissue to anchor the sleeve to the tissue, wherein at least one tissue anchor is placed within the distal sleeve-end-portion; and a contraction tool comprising an engaging element, wherein the engaging element is configured to be moved longitudinally into and through the lumen of the sleeve toward the distal sleeve-end, and to be reversibly coupled to the distal end of the contraction member, wherein when the engaging element is reversibly coupled the distal end of the contraction member, pulling the engaging element proximally increases a length of the distal end portion of the contraction member that is disposed within the lumen so as to longitudinally contract the sleeve. a flexible sleeve having a proximal sleeve-end, a distal sleeve-end, and a circumferential wall that defines a longitudinal lumen between the proximal and distal sleeve-ends; an elongate contraction member having a proximal end and a distal end, wherein the proximal end of the contraction member is attached to the sleeve at an attachment point of the sleeve, the attachment point and the proximal sleeve-end defining a proximal sleeve-end-portion, and a proximal end portion of the contraction member extends, in association with the circumferential wall of the sleeve, from the attachment point toward the distal sleeve-end and enters the lumen of the sleeve at an entry point of the sleeve so that a distal end portion of the contraction member is disposed within the lumen, the entry point and the distal end of the sleeve defining a distal sleeve-end-portion; and a plurality of tissue anchors configured to extend through the circumferential wall and into tissue to anchor the sleeve to the tissue, wherein at least one tissue anchor is placed within the distal sleeve-end-portion; and a contraction tool comprising an engaging element, wherein the engaging element is configured to be moved longitudinally into and through the lumen of the sleeve toward the distal sleeve-end, and to be reversibly coupled to the distal end of the contraction member, wherein when the engaging element is reversibly coupled the distal end of the contraction member, pulling the engaging element proximally increases a length of the distal end portion of the contraction member that is disposed within the lumen so as to longitudinally contract the sleeve.