The Collaborative International Dictionary of English v.0.48:

Futtock \Fu"ttock\, n. [Prob. corrupted fr. foothook.] (Naut.)
   One of the crooked timbers which are scarfed together to form
   the lower part of the compound rib of a vessel; one of the
   crooked transverse timbers passing across and over the keel.
   [1913 Webster]

   Futtock plates (Naut.), plates of iron to which the
      dead-eyes of the topmast rigging are secured.

   Futtock shrouds, short iron shrouds leading from the upper
      part of the lower mast or of the main shrouds to the edge
      of the top, or through it, and connecting the topmast
      rigging with the lower mast. --Totten.
      [1913 Webster]