What the standards setting actually measures
It is the horizontal distance from the zero line, the line level with the back of the box, to the crossbar. Every rule book measures it the same way. Push the uprights toward the pit and the number goes up, which moves the bar further from the box and demands more penetration to clear it. Pull them back toward the runway and the number goes down, which brings the bar closer to where a vaulter with a short takeoff is actually going to be.

