What do line umpires do in tennis?

Answer 1

Line Umpire

A line umpire stands at ready position, focusing on his assigned line.

The Line Umpire "calls all shots relating to the assigned lines." Line umpires work on court as part of a team of between one and nine line umpires. Each line umpire is assigned by the chair umpire to one line or, in the case of a short handed crew, a position in a system. For example, a line umpire on the receiver's side may have to cover the center service line then, following the serve, move to one of the sidelines. Line umpires are a requirement for professional tennis games.

The line umpire signals a ball out by making a verbal "out" call followed by the extension of the arm shoulder high in the direction the ball was out. A ball is signaled "safe" or "good" by holding both hands together knee high in front of the body.A line umpire who is unsighted and thus unable to call a shot (usually because a player obstructs his/her view) signals this by holding his/her hands beside his/her head, the upper side pointing in the same directing as the eyes; that call is then the chair umpire's responsibility

Answer 2

"Line Umpires" watch the lines or boundaries of the tennis court. They decide whether the ball lands in or out. However in a final arguement, the Chair Umpire has the final call.