What exactly is a Jewel Block??

[Sam Shapiro]

Pig Bodine's great-great-great grandfather just finished 'exercising' his 
penis in the ship's "jewel block"(p.55)....what is a Jewel Block?? I even 
checked my trusty HARBORS AND HIGH SEAS glossary of archaic nautical 
terms in Patrick O'Brian's books, and no luck there -- although that same 
book DID clear up the little mystery of what a "Spotted Dick"(p.56) is (no 
relation to the Jewel Block exercise)......help, someone......
Just read the National Review "critique" of M&D----ridiculous....it was 
almost as frustrating as John Leonard's smug, unreadable review in The 
Nation.......now, about that Jewel Block.....

--Sam Shapiro