ch is
yet to be determined. Both of these measurements must be accurate.
The boy on the end of the loose line moves it until the distance
between the two pieces of twine is exactly the length of your ten-foot
pole. The angle thus formed is exactly ninety degrees, or a right
angle. Having obtained one side and one end, to finish marking is
simply a matter of making the necessary measurements of a court as
shown on the diagram and marking each intersecting point with a nail
driven into the ground.

[Illustration: How to mark out a tennis court]

Another way to lay out a court is to drive two stakes or nails into
the ground 27 feet apart. (The line of these stakes should be the
position of the net.) Then take two pieces of twine, one 47 feet 5
inches long, and the other 39 feet. Fasten one line to each of the
spikes that you have placed 27 feet apart. Where the two lines meet
as they are pulled taut are the true corners of the court, as there
are only four points where they can meet. The various measurements can
then be marked as above by referring to the diagram. It is customary
to mark a double court and to indicate the lines for singles
afterward.

The game of tennis may be played either by two or four persons, or
sometimes an expert player will stand two beginners. The ball used is
rubber filled with air and covered with white felt and is 2-1/2 inches
in diameter. It is necessary to play with two balls, and to save time
in chasing those that go wild it is customary to play with three or
four.

One of the players begins by serving. The selection of the court is
usually chosen by lot or by tossing up a racket in a way similar to
tossing a cent. The side of the racket where the woven gut appears is
called "rough," and the other side "smooth." This practice is not to
be recommended, as it injures the racket. It is better to toss a coin.
The game of tennis consists in knocking the ball over the net and into
the court of your opponent, keeping up this volley until one side or
player fails to make the return properly or at all, which scores his
opponent a point. While a game in tennis consists of four points, the
simple numbers from one to four are not used. The points run 15,30,
40, game, when one side makes them all. Or it may be "15-30," "15
all," and so on, the score of the server being mentioned first. Where
one side has nothing their score is called "love." When one side has
scored four points the game is won--wit