• This shot is "out" for singles, but "in" for the doubles.Tennis Ball image by Jim Mills from Fotolia.com
  
  The general rules of competitive tennis relate to either singles or doubles matches. Singles matches simply pit one player against the other whereas doubles play a team of two players against another team in a slightly wider tennis court. Canadian doubles is a modification of competitive teams and court use when only three players are available. Canadian doubles is a slang term for this modified recreation play and is also sometimes referred to as Australian.
  
  

Two-Against-One

• Two-against-one is the basic premise of Canadian doubles. Players may choose this formation if they are one player short for a doubles match and want to keep everyone on the court. It is also used as a training method to help singles players learn to find more openings through the court while doubles players must learn to control angles and ball cutoffs.
  
  The basic rules of tennis apply where each team may only strike the ball once to return it to the other side of the court. The ball may be struck prior to bouncing or after one bounce.
  
  

Court Lines

• In Canadian doubles, the one-person team must cover the singles court designated by the interior sidelines. The width for the singles court is 27 feet wide. The two-person team must cover the designated doubles court, which consists of the singles court extended by 4.5 feet on either side with a "doubles alley." If the court does not have both the singles and doubles lines (some courts are strictly singles courts), Canadian doubles cannot be played.
  
  All serves must go to the designated service box with the server standing behind the baseline on the opposite side of the court. Once the ball is in play, the single player may hit anywhere in the court, including doubles alleys. The doubles team must only hit in the singles court.
  
  

Set or Game Score

• Since this is not an official match configuration, players have the choice of keeping the teams for an entire set or rotating the single person. If the teams are maintained for the entire set, each team alternates serving, with the doubles team alternating servers. When a set is played, the traditional scoring is used with the first team reaching six games winning the set.
  
  If players rotate to the single side, often the singles player is designated as the server to reduce confusion and give everyone a chance to serve. In this format, only the single player serves; the doubles team always receives the serve. Each player tallies his winning games at the end to see who amassed the most games through a rotation. This rotation of serve is what is sometimes referred to as Australian doubles.