1) Assistant referees 2) Some grid officials 3) Tennis officials 4) They assist referees 5) Wimbledon official 1) Cast 
the 2 officials who assist the referee in making his decisions; they monitor the sidelines and goal lines to determine when a ball goes out of bounds and they carry a flag to signal their observations.
The two officials on the ice, one toward each end of the rink, responsible for infractions of the ru
[Ice Hockey] the two officials on the ice, one toward each end of the rink, responsible for infractions of the rules concerning off-side plays at the blue lines or center line and for any icing violations; they conduct most of the face-offs, sometimes advise the referee concerning penalties, and separate players who are figh...[Soccer] the 2 officials who assist the referee in making his decisions; they monitor the sidelines and goal lines to determine when a ball goes out of bounds and they carry a flag to signal their observations.