The thumb screw is for nozzle head. It screws into the top of the head and holds the air stem in place. All of our nozzle heads come standard with a thumb screw.
Western part: 1400 650 030. One size fits all our nozzles.
Putzmeister part: AT301845.
Thumbscrew for 1" , 1.25" and 1.5" Nozzles