Quick answer: Contact on the ball's equator or above; on video, chest height rises before impact or the lead arm arrives bent.
What it does to the ball
A low screamer along the ground, with no distance control and no ability to hold a green.
Root causes (by frequency)
Standing up in the downswing (loss of posture or early extension)
Trying to lift the ball with the wrists
Ball too far forward in the stance
How to fix it
Keep your chest height until after impact: stay in your posture and cover the ball on the way down
Drills that fix it
Chest at the same height · 15 min · 15 reps
Stay in your posture until after impact Record face-on and mark your head height at address with a line on the screen. Hit balls at 70%, checking that your head doesn't rise before impact. The feeling is of covering the ball with your chest on the way down.
Frequently asked questions
What is "Thin contact (thin / top)" in the golf swing?
Contact on the ball's equator or above; on video, chest height rises before impact or the lead arm arrives bent.
What does thin contact (thin / top) do to the ball?
A low screamer along the ground, with no distance control and no ability to hold a green.
How do you fix thin contact (thin / top)?
Keep your chest height until after impact: stay in your posture and cover the ball on the way down