I will take a picture of the boom hanger (Herreshoff term), the modern term is gooseneck, and upload it. It has a knurlled knob that screws in to put pressure on the sail track to hold it in place, however, if you wanted to adjust the tension on the luff of the sail an keep it, I don't think the knob would be enough to hold it, so I think you would attach some type of vang or something to cleat if off further down the mast.