Spindle Castle Nut, 6 Point 1" Threaded Area on Spindle Purpose: Holds Idler Hub or Brake Drum Hub in place on axle. Adjustments: Turn Nut Clock Wise until Hub is locked down, then back off just enough to allow Hub to turn without binding. Insert Cotter Pin and bend down toward inside of trailer to avoid contact with rubber grommet in dust cap. NOTE: Castle Nut may need to be turned slightly to align holes in spindle with castle opening. Depicted as first Nut on Left in Picture.