Players must change ends of the court when the games add up to an odd number. This keeps the match fair so that both must face elements, i.e., wind, sun, shade. The time limit on a changeover is 90 seconds.

There are two basic ways to switch sides in tennis. The first is when players switch from one serving side to another after each point. The other is the changeover, where players completely switch sides during designated times in a match. It's among the tennis rules set up to ensure fair play.

Switching Serving Sides

Games start with the server on the right side of the court behind the baseline, usually at the center mark, serving into the receiver's left service box. After a point, the server switches to the left side of the baseline, often just a hop over the center mark, to serve into his opponent's right service box. This back-and-forth continues until a game is won. The next game starts with the server on his right side again.

Changeovers in a Match

A player has to win six games, and at least two more than the foe, to claim a tennis match. Players switch sides after every odd game, as in the first, third and fifth games, and so on. Players also switch sides at the end of a set if they're playing an odd number of games. If the total is even, players switch sides after the first game of the subsequent set.

Tiebreaker Changeovers

Two different types of tiebreakers -- one used in major tournaments and another sometimes used in United States Tennis Association play -- both require frequent changeovers. The first is the classic 12-point tiebreaker when the set score is tied at six games. The first player to win seven points and be two points ahead wins the set. Players switch sides after every six points. The Coman tiebreaker works the same way except players change sides after the first point and every subsequent four points.

Rest Rules

Rest periods aren't allowed for the first changeover or during tiebreakers. Between those extremes, players can take 90-second changeover breaks during a game and 120 seconds between sets. Changeover time can double as a bathroom break, as men are allowed only one bathroom visit per match, ladies two, but players have to be back on the court in 90 seconds. The rules also forbid electronic device use during a changeover, but some pros hide under towels and sneak a peek at their phones, according to the "New York Times." Former world No. 1 Jim Courier famously read a novel during a changeover.