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 red stone has a certain connection to the bottom, using only the shaded hexagons, even if blue moves first.
Countless edge templates can be constructed, all of them of varying degrees of usefulness and frequency of occurance.
