A tall player and a shorter player serve from different-looking positions, yet the current fixed-height service rule gives them the same reference. The measurement concerns the shuttle at the instant it is struck, not where the server’s waist happens to be.
Under law 9.1.6 in the BWF Laws of Badminton, the whole shuttle must be below 1.15 metres from the court surface at impact. The wording concerns the whole shuttle, not just its base or the hand holding it.
Keep the reference fixed
Imagine two players of different heights standing on the same court. The permitted height does not move upward for the taller player. Equally, lowering the hand after contact does not change where the shuttle was when it was struck.
Older explanations may refer to the server’s waist. Check the rules adopted by the competition and the edition being discussed before combining instructions from different periods or local formats.
A replay can hide the measurement
A camera looking upward or across the court can make relative heights difficult to judge. A cropped social-media clip may also omit the exact contact frame. Those limitations are reasons to be careful about declaring an official decision wrong from appearance alone.
For supervised practice, ask a qualified coach or official how to use a suitable height reference without creating an obstacle or changing the service action. Do not rely on an arbitrary mark on clothing as though it were the rule’s fixed measurement.
Height is only one part of a correct service. The other service requirements still apply, including the initial contact with the shuttle’s base and the relevant positioning and movement provisions. A low strike does not automatically make every other part legal.
When explaining a call to another player, identify the specific requirement and moment involved. “The whole shuttle at impact, measured from the court” is a clearer starting point than comparing the server’s body position with that of a player of another height.