A futtock plate is, I believe, an iron plate attached to the top of a ship's mast. But I don't know much about this subject.
我觉得内龙骨翼板是指船桅杆上端的铁板。我对这东西不太了解。
英语百科
Futtock shrouds
(重定向自Futtock)
Futtock shrouds are rope, wire or chain links in the rigging of a traditional square rigged ship. They run from the outer edges of a top downwards and inwards to a point on the mast or lower shrouds, and carry the load of the shrouds that rise from the edge of the top. This prevents any tendency of the top itself to tilt relative to the mast.