These groove ring wax seal finishes, appear when looking down at the rim of the finish to be two circular and parallel ridges with an indented groove separating them. This groove was called an "annular groove" by early glassmakers. The rounded outside edge of the finish slopes down and towards the upper edge. The aqua glass finish image below shows the groove structure of this finish type. This design allowed wax, wax-dipped string, or other sealing compounds to be placed into the groove.