Two dry rouge wings are drawn inward from the sides. Slide both fingers closer and release to lock the span. Inside the powder band it counts, and the heart of the band counts more fully. Overshoot or a miss cracks the powder once; three cracks scatter it. The wings carry inertia, and the band can jump. There is no separate lock. The release is the decision. Warm dust stays light, and pace lives in how fast the wings close. This is not a stopped needle and not a pair of rulers. It is one opening of the hands after both wings have come near.
Pinch rouge wings inward and release inside the powder band.