A shank is how jewelers refer to the back of your ring -- its band. This is another one of those parts of a ring that can wear out over time.
I know it seems frustrating! It's gold, why does it wear out? You might wonder...
Gold, by nature, is soft. In fact, it is softer than opal! Sadly, the very quality, malleability, which makes gold submit to our design processes, also makes it subject to wearing down over the years.
So! Over time, shanks get thinner simply from normal wear. As a result they can bend out of shape and even break. This is especially common with rings that were originally designed with a thin, slender shank.
Once your shank gets too thin from wearing, the best solution to have your jeweler replace it with one that is thicker and more durable. The old thin shank is cut away with a saw and a new, thicker and wider section is custom made and soldered into its place.