Wiktionary
racking bend
n. a type of bend knot used to join the ends of two lines or ropes of very different thicknesses.
Wikipedia
Racking bend
The racking bend is a knot for joining two ropes of different diameter. "Racking" refers to the figure eight weaving that binds the bight of the larger rope together.
It serves a somewhat similar purpose as a Sheet bend, a Double sheet bend or a Heaving line bend, and may be used to throw a thick line over with the help of a thinner line at the end of which there may be a weight such as a Monkey fist or a Heaving line knot.