I thought I would look this up, and here is one for the ages:
A ring on a batter’s thumb helps to ensure that the batter is poured evenly and smoothly into the pan. The ring also prevents the batter from sticking to the spatula, making it easier for you to cook your dish correctly.
Make sure that you always use a fresh ring when preparing batters, as old rings can cause them to become thick and difficult to work with. If your batter starts to stick to the pan or spatula, try adding more liquid or Amend until it becomes smooth again.