Edge template
From HexWiki
An edge template is a pattern which guarantees a connection the edge. Here is an example of a third-row edge template (template IIIa, also known as the Ziggurat):
The cells marked by a star are irrelevant to the template, and can be occupied by either player, or can be empty. Even if Blue moves first, there is no way he can prevent from connecting to the bottom.
Countless edge templates can be constructed; some of them happen frequently and everybody should be familiar with them. Some are less frequent, but can still be useful to know.
