main-truck

plural main-trucks

1. nauticalOn a wooden mast, a circular disc (or sometimes a rectangle) of wood near or at the top of the mast, usually with holes or sheaves to reeve signal halyards; also a temporary or emergency place for a lookout.

   But oh! shipmates! on the starboard hand of every woe, there is a sure delight; and higher the top of that delight, than the bottom of the woe is deep. Is not the main-truck higher than the kelson is low?

   1851 November 14, Herman Melville, “chapter 9”, in Moby-Dick; or, The Whale, 1st American edition, New York, N.Y.: Harper & Brothers; London: Richard Bentley, →OCLC

   1 more example

   I told him about everything I could think of; and what I couldn't think of he did. He asked about six questions during my yarn, but every question had a point to it. At the end he bowed and thanked me once more. As a thanker he was main-truck high; I never see anybody so polite.

   1913, Joseph C[rosby] Lincoln, chapter IV, in Mr. Pratt’s Patients, New York, N.Y.; London: D[aniel] Appleton and Company, →OCLC