Meaning of jewel block in English:

jewel block

Pronunciation /ˈdʒuː(ə)l blɒk/

noun

Nautical
  • A block suspended on a pendant at the end of a spar, used to alter the direction of a line, rather than for mechanical advantage; especially each of two such blocks at the extremities of the main and fore-topsail yards, through which the halyards of the studdingsails pass.

Origin

Mid 18th century; earliest use found in William Falconer. From jewel + block, so called on account of its hanging like a jewel on the pendant at the end of a spar.