That's right. You rotate the shaft to a different axis, then take your fingers off. The plunger on the dial indicator moves up or down according to how much the weight makes the shaft flex along each axis you check, and that makes the needle on the dial move. Read the dial to get the measurment. If the shaft's spine was perfectly consistent the indicator would read exactly the same at each axis. I haven't checked any carbon arrows in a long time but, 5-6 years ago I saw variations up to .035" in spine on the same shaft on medium grade carbons from several different companies. Hopefully they've improved somewhat since then.