Actually, the rings provide an area for the glue to be placed.  As the can
rolls over the glue applicator it then immediately rolls over a label and picks
up the label before turning back on its end.  This prevents the label from
peeling off easily.  I know this since I ran the label machine and filled the
glue pot for the Libby canning factory in Rochester, MN for my high school
summer job.

Julie Schablitsky



Quoting Ron May <[log in to unmask]>:

> I expect the "rings" also served to strengthen the can, much like
> corrugation
> strengthens sheet metal in construction or cardboard for boxes.
>
> Ron May
> Legacy 106, Inc.
>