The rigger I use (Dave Thompson of Eggars Sails) showed me the Harken system SWG posted above and then made up his own kit; nicopressed the cable fittings and sold me the blocks, cleats and line. Most important he explained how to do everything; measuring the placing of the fittings, tapping and threading the holes for mounting the fittings on the mast and boom, setting it up and using it. He saved me a lot of money.
It works very well; It is out of the way when sailing, deploys easily and keeps the main in check. An absolute necessity for single handing.