Rule 13 of 25 · Chapter II — The Strike
Strike the ball toward the centre of the face and low on it, and verify with face spray rather than feel.
Why this rule exists
Iron distance is decided as much by strike location as by swing speed — a groove or two toward the toe or high on the face costs yards you will never diagnose from ball flight. Feel is unreliable here: most players cannot tell a centre hit from one half an inch out, and gear effect masks it. Spray turns an invisible variable into a picture you can act on.
In practice
Dust the face with foot spray, chalk, or dry-erase marker and hit five to ten shots, then read the pattern rather than any single mark. You want a tight cluster around the centre and slightly below it, where iron faces transfer energy best. If the pattern sits high, check your low point; if it drifts toward heel or toe, check ball position and distance from the ball before touching your swing.
When it doesn't apply
Spray marks on the face are for practice, not competition — check your local rules before applying anything in a round. And ignore the pattern from a handful of swings if the lies were uneven or you were working on something new; you need a stable sample to trust it.