Edge template IV3a
From HexWiki
Template IV3-a is a 4th row edge template with 3 stones:
If the middle red piece is removed, the template stays valid, as long as the two remaining stones are connected to each other in some other way.
(From: www.drking.org.uk)
Defending the template
Red has two main threats:
and
For trying to block the connection Blue has to play on the overlap:
If Blue plays at x:
Red 4 is connected to the top by the two cells marked with +.
If Blue plays at y: