fly block

noun

, Machinery, Nautical.

1. (in a Spanish burton or the like) a block, supported by a runner, through which the hauling part of the fall is rove.
2. any block that shifts with the movement of its tackle.

Word History and Origins

Origin of fly block¹

First recorded in 1835–45

Example Sentences

NASA’s plan was to fly Block 1 just once for the first SLS flight, and then fly Block 1B.

From The Verge