snatch block

a fairlead having the form of a block that can be opened to receive the bight of a rope at any point along its length.

Origin of snatch block

First recorded in 1615–25

snarl-up, snarler, snarly, snash, snatch, snatch block, snatch squad, snatchy, snath, snazzy, sncc

It is called a snatch-block and often employed for drawing water from wells, or for hoisting light weights.

The Library of Work and Play: Mechanics, Indoors and Out |Fred T. Hodgson
Turn that snatch-block, Cully, and tighten up the watch-tackle.

Tom Grogan |F. Hopkinson Smith
Davy, the boy, led the warp through a snatch-block fixed to the mast-hole on to the capstan.

The Deemster |Hall Caine
It was Danny Fayle's duty to lead the warp through a snatch-block fixed to the mast-hole on to the capstan.

She's All the World to Me |Hall Caine

A snatch-block is a single block having a notch in one cheek to receive the bight of a fall.

The Gunner's Examiner |Harold E. Cloke

snatch block

nautical a block that can be opened so that a rope can be inserted from the side, without threading it through from the end

C17: so called because the rope can be inserted quickly: figuratively, the block snatches it. See snatch