There are three kinds of traps used, called the ground, spring, and plunge traps; the former is so arranged that when the string is drawn, the trap, which is composed of tin plates, falls over and lies flat on the ground; while the others, through the instrumentality of a spring, or by a vigorous jerk on the line, throw the birds into the air. The ground-traps are considered by many the most scientific, leaving the shooter in doubt as to the direction of the bird’s flight, and preventing his shooting on the calculation which can be made very accurately with a spring-trap--that the bird will invariably be thrown to a certain place, and may be killed there, nominally on the wing, but before he has really got under weigh; but in the West the plunge-traps are generally preferred, as they insure the bird’s flying at once. The traps are also spoken of as “H and T,” or “head and tail” traps, and are usually marked with a large H or T; but this means merely that the shooter may select the trap to be pulled by the toss, in case the terms of the contest permit it. The sportsmanlike mode, however, as claimed by Eastern sportsmen, is to allow the trapper, provided he can be perfectly relied upon, to pull any trap he may choose, without notice to the shooter. Four or five traps are generally used, placed several feet apart, at twenty-one yards from the score in single-bird shooting, and at eighteen yards in double-bird shooting. In double-bird shooting the two birds are not placed in the same trap, but two traps are pulled at the same time. In single-bird shooting only one barrel can be discharged at one bird; and to save time, the shooter should fire at two birds, one after the other, before he leaves the score, being thus compelled to use both barrels of his gun. A bird, to be credited as killed, must be retrieved within the bounds--that is to say, must be gathered with the hands alone; and it was formerly permitted to take him not only on the ground or in the air, but from a tree, and the shooter might walk round a running bird and drive him towards the trap; but more modern rules require that the bird shall fall, and shall be proceeded to straight from the score. The bounds are eighty yards radius from the centre of the traps in single-bird shooting, and one hundred yards in double-bird shooting. The distance should be measured with a rope, and marked by small flags or painted stakes set up in the ground. The judges order the shooter to retrieve any bird they think proper; and in case there is doubt whether a bird was hit, although duly retrieved, they must examine and decide, being occasionally compelled to pick the feathers in order to ascertain.