It sounds like a roller reefing boom. They used to be as common as dirt as almost every production boat from the mid-1960's until the mid-1970's had one. It was a lousy system. It took forever to crank in a reef because the halyard had to be eased a little bit at a time (a serious problem when coupled with the reel winches that were popular during this period) and then take a crank on the reel winch. There was no way to tension the foot as the sail was rolled in. Wedges or throwing a coat into the roll would not help since the leech of the sail will still creep foward as rolled. Sails of that era were cut with almost no broadseaming and without a shelf foot, but modern sails would not work at all on a roller reefing boom.
My best advice is to go to a two line, slab reefing system. Its fast, cheap, reliable and it allows independent luff and foot adjustments.