Rules

34. The Doubles Court
For the Doubles Game, the court shall be 36 feet (10.97m.) in width, i.e. 41/2 feet (1.37m.) wider on each side than the Court for the Singles Game, and those portions of the singles side-lines which lie between the two service-lines shall be called the service side-lines. In other respects, the Court shall be similar to that described in Rule 1, but the portions of the singles side-lines between the base-line and service-line on each side of the net may be omitted if desired.

USTA Comment: The Server has the right in doubles to stand anywhere in back of the baseline between the center mark imaginary extension and the doubles sideline imaginary extension.