Checking the balance points on the raw shafts, on another sophisticated and expensive piece of equipment; a piece of cardboard tacked to the back of the arrow rack.

Lay the shaft on the jig and nudge it back and forth until it balances, then mark with chalk and measure the balance point.

This identifies if they have a "heavy end". If they balance more than 50% of the way along, flip them so that the heavy end is up in the rack.