Rule 14 of 25 · Chapter III — The Motion That Delivers It
Build the backswing by turning your chest away, not by lifting your arms.
Why this rule exists
A chest turn stores width and depth that the downswing can use; lifting the arms puts the club steep and behind your hands with nowhere to go but down and across. Arm-lift backswings also change length every time you swing, so your low point moves and you catch the ball thin one shot and fat the next. Turning is easier to repeat than a hand-and-arm position you have to feel for.
In practice
Feel your lead shoulder move across your chest and your trail hip take the pressure while your arms stay quiet and connected to your torso. Check length in a mirror or on video: at the top your hands should have arrived because your body turned, and the club should feel like it weighs almost nothing. A short, full turn beats a long, floppy arm swing — most golfers hit better irons with the hands no higher than the trail shoulder.
When it doesn't apply
If restricted mobility, injury, or age caps your turn, some arm lift is how you get the club up at all — keep it symmetrical and quiet rather than forcing a rotation your back won't allow. On short pitches and knockdown shots you deliberately shorten the backswing and rotation both.