The Explainxkcd for this lead me to the Wikipedia article for Block and tackle, which lead me to Block (sailing), whose first paragraph is giving me Plumbus vibes:

In sailing, a block is a single or multiple pulley. One or a number of sheaves are enclosed in an assembly between cheeks or chocks. In use, a block is fixed to the end of a line, to a spar, or to a surface. A line (rope) is reeved through the sheaves, and maybe through one or more matching blocks at some far end, to make up a tackle.