Well supposedly once the wash is sugared up and prior to pitching a well heeled extractor is supposed to check it with the gauge. Then you try to find somebody sober enough to write that figger down somewhere where you can find it later and it will be safe. Then you check it again when you think its finished looking and tasting right..and find somebody to use arithmetic to substract the low reading from the high and come up with some meaningful data. I always forget to check it to start with..plust it hard to get help around here. I cant see the little squiggly lines and small numbers too well. I treat it like a boat. Only with this boat the more it sinks the better it is. Know 1.006 is floating high and way to sweet. When it daubs down to 1.001 or 1.000 is the best maybe. Looks like snake eyes when it gets right. Now sometimes it hits high in the water and refuses to sink. That is called a screwed up ferment..lol. After a reasonable mourning period think it good to run it and get a little bit and use that to chill out enough to determine the error so as to not do it all over again yet another time. Which a person could do all that without a gauge. When mine breaks doubt I will bother to buy another..less a pal brings me a free one..lol. They way over rated in other words. Hope this helps. The only bright side is the gauges seem to have got cheaper over the years. Like LCD watches and compooters etc.