Rule 5 of 25 · Chapter I — Before You Move
Match stance width to club length: about hip-width for wedges, about shoulder-width for long irons.
Why this rule exists
Stance width trades stability against turn. Too narrow with a long iron and you lose your base at speed; too wide with a wedge and you restrict the pivot, which pushes you to lift and drop the club instead of turning through it. Width also affects how easily your pressure can move to the lead side, which is what puts the low point forward.
In practice
Measure with your heels: wedges roughly under your hip joints, mid-irons a little wider, long irons close to shoulder width on the outside of the feet. Hit a few shots at each width and notice which one lets you finish balanced with the trail heel off the ground. Once you have found your widths, use them consistently rather than reinventing the stance for every shot.
When it doesn't apply
Widen and lower for windy conditions or steep slopes, where balance outranks turn. Narrow the stance for short, controlled shots where you are deliberately reducing distance and body motion.