I believe the system shown below is copied from an Abbott Soling. It is nicely self-contained and can easily be operated by the crew who tightens the outhaul by pulling on the rope end with the ball that hangs down. Of course, as with all outhauls, it becomes difficult/impossible to tighten in proportion to the amount of wind and vang pressure being exerted on the mainsail! To uncleat and loosen the outhaul, the crew reaches between the bullet block and the cleat, grabs the rope and pulls it out of the cleat: