A drain-cleaning spray nozzle attaches to the end of a high-pressure hose and is inserted into a drain or sewer pipe. It uses pressurized water jets to break up blockages, propel the hose deeper into the pipe, and flush or scour the interior pipe walls.
Rear-facing jets push water backward, which pulls/propels the hose forward into the pipe.
Forward-facing jets (in some nozzles) are used to cut through blockages (roots, hardened scale, grease) ahead of the nozzle.
The spray angle and number of jets affect the thrust (how fast/hard the hose goes forward) and cleaning effect (how well the pipe walls are cleaned).
After pushing through the blockage, the hose is usually pulled back slowly so that the same jets flush the loosened debris out and clean the pipe walls.