For me, i think the hook gauge is the easiest way, just slide the hook through the holes until you find the right fit. If you don’t have one, a caliper works too, then you can match the measurement to a hook size chart.I've got a handful of vintage crochet hooks. Some are bone, some plastic, but the size markings are completely worn off. What's the best way to figure out their sizes? Is there a specific gauge tool or trick you all use?