SELF-LOCKING WINCH

A system includes a transcatheterally-advanceable driver and an implant. The implant includes a winch, and a tether that has an end portion. The winch includes a spool, a mount, and a driver interface engageable and drivable by the driver. The mount is coupled to the driver interface such that driving of the driver interface by the driver rotates the mount about a rotation axis. The spool is coupled to the tether, and defines a spool axis that is non-coaxial with the rotation axis. The tether extends away from the winch toward the end portion. The spool is fixedly coupled to the mount such that rotation of the mount about the rotation axis draws the end portion of the tether toward the spool by winding the tether around the spool axis of the spool. Other embodiments are also described.