The first thing to know about a trap field is that it's lopsided on purpose. One small building — the trap house — sits out in the middle, and everyone shoots toward it from behind. Inside that house is a single machine that throws clay disks downrange at about 40 mph, swinging left and right between shots so no one knows exactly which way the next one will go.
What changes from shot to shot isn't the clay. The clay is always the same disk, leaving the same machine, inside the same horizontal cone of possible angles. What changes is where you're standing when it leaves.
In singles, all five shooters in a squad stand on a 24-foot arc that sits 16 yards behind the trap house. That arc has five posts on it, labeled P1 through P5 from left to right. The 16-yard line is fixed by the rules of the sport; the arc, the five posts, and the machine in front of them are the same on every American Trap field in the world.
The reason it matters where you stand: the trap machine doesn't know about you. It picks an angle from its cone and throws. If you happen to be standing on the far left of the arc, an angle that would look like a "straightaway" to someone in the middle now looks like a clay heading away to your right. Same clay. Different geometry.
A quick tour of the five posts
P1, hard left. The leftmost post. From here the trap house is off to your right, and most of the angles the machine throws will send the target away to your left or straight out in front of you. The occasional clay heading toward the right edge of the cone will look like a gentle right-quartering bird. P1 is a left-shooter's post — most of your shots are left or straight.
P2, left-of-center. Step one post to your right and the picture rotates a little. Hard left-angle birds are still there, but the straightaways are more common and the rights start to show up as real right-quartering targets instead of mild ones.
P3, dead center. From the middle post, you sit directly behind the trap house. You see the widest variety of angles of any post on the field — extreme lefts, extreme rights, and everything in between. P3 is where the trap machine's full cone fans out symmetrically in front of you.
P4, right-of-center. A mirror of P2. The rights dominate; lefts arrive as quartering birds. If you understand P2, you understand P4 — flip everything left for right.
P5, hard right. A mirror of P1. Most shots head out to your right or straight away, with the occasional left-quartering clay that looks gentle from where you're standing. P5 is a right-shooter's post.
Why you'll shoot all five in one round
A round is 25 birds: five shots at each of the five posts. After everyone in the squad has taken their five shots from their current post, the whole squad rotates one position to the right, and the next five begin. The shooter who started at P5 walks all the way around the back of the squad to P1. By the end of the round you've stood on every post on the field.
This is why "where you stand changes the game" is the one sentence every new trap shooter eventually internalizes. The clay is the same. The call of "pull" is the same. But P1 in your first round of the day and P3 in your fourth round are two different shooting problems, and your scorecard will tell you which one you've gotten comfortable with.
Once the field stops feeling like a row of identical pegs and starts feeling like five small, separate sub-games, you've already absorbed the most important thing a new trap shooter can know. The rest is repetition.