snatch block

noun2

1. •
   A kind of block with an opening in one side to receive the bight of a rope.
2. •
   A block equipped with a hook that hooks a cable so that it can be doubled back on itself in order to double the load carrying ability of the cable.

   • On a tramway installation, drag the haul rope through each intermediate tower, placing it in the snatch block as the tower is passed to lighten the load. — 1964