The playing surface of a tennis court for singles is 27 × 78 feet, and for doubles 36 × 78 feet; but as a double court contains all the lines for singles it is usual to mark out for doubles at the beginning. Back of the outer line there must be a space of from 15 to 20 feet to the stop-nets, and at the sides there should be at least 6 feet, preferably 10 or 12 feet, beyond the line of the double court. This permits free access to the courts on either side of the net, and also allows room for players when volleying. This is the reason why a space of 60 × 120 is generally considered necessary for a good tennis site.

The marking of a court must be exact. First determine the position of your net in the middle of the site, and then lay out the single court. Place two pegs temporarily in the ground 27 feet apart and make a line there to represent the net. Then measure off two lengths of string—one 39 feet long, and the other 47 feet 5 inches. With these two lengths you can make your courts exactly right.

Lay the shorter length of string on the ground approximately at right angles to one of the net pegs; then start the longer string from the opposite peg and run it diagonally across until it reaches the end of the 39-foot string. At that point drive in a corner peg. You have a right-angled triangle that is absolutely exact. Repeat this operation to get the other corner, and then obtain the corners for the other side of the net in a similar way. With the corner pegs in place, proceed then to measure off from the net peg 21 feet on the 39-foot line. That point marks the end of the service line, and a straight line drawn across it will intersect in the middle the diagonal lines.

For the double courts prolong the net line 4 feet 6 inches, and join this to the points at the end to form alleys. The double courts are then finished except for the central line. This is obtained by measuring off the middle of the service lines and connecting them with a straight line through the center.

As there is quite a little bother in measuring off the courts, it is quite essential that the corner points be made permanent. Small stakes or pegs should be driven into the ground at the corners deep enough so they will not trip players. Nearly every heavy rainstorm washes away the lines so that remarking is required. On clay courts white paint is sometimes used for marking, as this will last longer than whitewash, but at the best, remarking must be done quite frequently. Paint is not suitable for grass courts on account of the injury caused to the grass roots. Portable white marking tape is sometimes used. This is held down by staples and double-pointed pins, but there is always the danger of the tape tripping a player.

Markers have been devised for facilitating the lining out of tennis courts. These consist for the most part of an iron or tin receptacle on wheels, with a marking wheel in front on which the contents are sprayed continually. Marble dust or slaked lime can be used in these markers. They give a uniform width, and one can mark off the lines as fast as he can walk. Home-made markers can be made by inverting a tin can and closing the mouth except for a tiny hole through which the liquid can flow. An ordinary wheel with a flat rim one inch in width is made to revolve in front of the mouth of the can so it will catch the drippings of the liquid. Mounted on an axle with handles this contrivance is pushed before the operator.

On a grass court none of these methods of marking are equal to grass itself. At the time the seed is sown on the court, plant freely in some part of the garden the seed of the crested dogtail grass. This grass is yellow green to white, and if sown very thickly it will serve to mark the courts. When the grass on the court is high enough for cutting transplant the crested dogtail grass to the lines marked out.

Mark out the courts exactly with tape or string, and then cut out on one side of it a strip of sod two and a half inches wide. This strip is then filled with the sods of the dogtail grass raised in the garden for this purpose. The sod should be patted down firmly in place, and a few seeds of the dogtail grass sown in with it. In this way you have the courts marked out permanently by grass, and the contrast in color is sufficient for all playing purposes. The effect, of course, is very striking, and far ahead of the courts that have to be whitewashed after every rainstorm.

The dogtail grass is a hardy grower, and it will, if not controlled, spread out into the court itself. This, however, can be prevented by an occasional weeding. It must be kept in its narrow strip even if roots have to be pulled up at times. If the spreading roots crowd out the green grass, the latter can be renewed by planting a little sod from some other part of the garden.