Your tennis serve, measured from toss to contact.

How high your tossing arm reaches at its peak — read from your arm, not the ball. A long, tall toss arm is the platform the serve stands on.

Whether your tossing arm stays long at the trophy. A straight arm tosses with the shoulder, and that’s what makes the toss repeat.

The time from your tossing arm’s full reach up to the hit. Enough for a real trophy, not so much that you’re waiting under a moonball.

The bend in your hitting arm at the trophy. Around a right angle stores the throw; a straight arm at this checkpoint has nothing left to release.

Where your hitting elbow sits against your shoulder line at the trophy — level is the checkpoint. A drooping elbow is the first domino of the tray.

Whether your wrist actually falls below your elbow behind you — the fold that lets the racquet head drop. If this never goes positive, the serve is a push, not a throw.

Toss arm up, racquet arm cocked with the elbow at shoulder height, knees loaded - hold the trophy for 3 seconds in a mirror. Make the checkpoint a home, not a blur.

Lay a racquet on the court at 1 o'clock inside the baseline. Toss and let the ball drop - it should land on the strings. Catch-height tosses, stiff arm, fingertip release.

Start AT the trophy position and serve from there - no wind-up. Isolates the drop-and-drive so the racquet learns to fall before it flies.

From trophy, let the racquet head fall behind your back (the 'back-scratch'), then throw it up at the ball. The drop is gravity's job - your job is to not interrupt it.