 One clip is fastened to the diver's harness, and the other is used to fasten the line to the shot line or anchor line.In current this relieves the diver from holding on to the line during the decompression stop, and the horizontal length of the line will absorb some or all of the vertical movement of the shot line or anchor line due to wave action.The jonline is named after Jon Hulbert, who is credited with its invention.