NOVELTY - A main sail reefing system has a reefing mechanism (40) including a drum assembly (200) with two rigidly connected coaxial top and bottom drums (210,220) for collecting luff end reefing lines (31) and leech end reefing lines (32), a drive mechanism for rotating the drum assembly, and a level wind mechanism (110) mechanically coupled to the reefing mechanism for coordinating movement of the line guides (112) with rotation of the drum mechanism.    USE - Main sail reefing system e.g. for use in sail boats.    ADVANTAGE - Enables single control line to pull two reefing lines down to main sail boom, minimizing amount of line as well as number of lines that must be hauled into cockpit to deploy reef. Total mechanical load produced by reef is split between separate reefing lines on main sail and brought together again at drum assembly, spreading out and minimizing loads on sail while allowing system to be operated by single control line led from drum assembly to cockpit. Enables cockpit line to be pulled out from center drum, equipped with threaded disc, and transition to threaded disc during reefing process, providing extra leverage during out-haul tensioning of main sail. Level wind mechanism is simply constructed of extrudable rod and tube profiles fastened together with machine screws, reducing material wastage and machining costs to minimum, at same time eliminating need for welds usually leading to heat-related distortion of close fitting components. Drum assembly may be constructed by securing all drums to single tube of e.g. extruded aluminum, allowing for lower manufacturing costs. Leverage battens may be attached to center drum to increase its diameter, further increasing leverage available during reefing process.    DETAILED DESCRIPTION - A main sail reefing system has a reefing mechanism (40) including a drum assembly (200) with rigidly connected, coaxial top and bottom drums (210,220) for collecting luff end reefing lines (31) and leech end reefing lines (32), a drive mechanism for rotating the drum assembly, and a level wind mechanism (110) mechanically coupled to the reefing mechanism for coordinating movement of the line guides (112) with rotation of the drum mechanism. The level wind mechanism includes a camshaft for rotational to reciprocating motion conversion, and line guides mechanically coupled to the camshaft and reciprocated across the widths of the drums to guide the reefing lines onto the respective drums. A center drum (230) is attached coaxially to the two drums and is coaxially attached at one end with a large diameter threaded disc (240) e.g. LeverDisc(RTM: not defined). An INDEPENDENT CLAIM is also included for a method for reefing a main sail.    DESCRIPTION OF DRAWING(S) - The drawing shows the side view of a reefing mechanism with a large diameter threaded disc.    Luff end reefing lines (31)    Leech end reefing lines (32)    Reefing mechanism (40)    Level wind mechanism (110)    Line guides (112)    Drum assembly (200)    Top and bottom drums (210,220)    Center drum (230)    Threaded disc (240)