futtock plate

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An iron plate attached horizontally to the top of the lower mast to secure the topmast rigging and the upper ends of the futtock shrouds.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun nautical A plate (usually metal) attached horizontally near the top of the lower mast of a square rigged ship in order to secure the topmast. Rigging runs both upwards (topmast rigging) and downwards (futtock shrouds) to maintain stability.