Second order template

A second order template, is a pattern which guarantees a connection even if the opponent is given a free move at the beginning. Put another way, a second order template is a pattern in which an intrusion is not a forcing move. A pattern can be proved to be a second order template by showing that every possible intrusion preserves at least one first order template.

Examples
R2 C3 Sa1 Vb1 Vc1

Third row
R3 C6 Sa1 Sb1   Vd1 Ve1 Sa2

This pattern can be reduced to ziggurats:

R3 C6 Sa1 Sb1 Pc1 Vd1 Ve1 Sa2 Pb2 Pc2 Pa3 Pb3

R3 C6 Sa1 Sb1   Vd1 Ve1 Pf1 Sa2           Pe2 Pf2 Pe3 Pf3

Therefore the only forcing moves must lie in the overlapping area. However, the overlapping is alson non-forcing thanks to Vertical's (1) moves. R3 C6 Sa1 Sb1   Vd1 Ve1 Sa2 V1b2  Pd2     V1f2 Pc3 Pd3

Usage
A first order edge template prove that a group is connected to the edge provided the player answer threats made to the connection. If the player wants to preserve the connection, the opponent can throw stones in the carrier that will later serve as ladder escapes, such moves belong to the category of double threats. Recognizing second order edge templates helps to know whether an area is safe or might be subject to such double threats.