Well, waaaay back in the day, that’s how you brewed. When the kreusen fell, you put your hydrometer in the open 12 gallon crock of beer. The hydrometer had a red line on it. When it got down to the red line you bottled. As a broke, thirsty college student, I made 1500 gallons of beer that way. Don’t ask how long ago that was. Yes, I did graduate. 