Creo Interactive Surface Design (Style) > Connections > Surface Connections > About Surface Connections with Triangular Surfaces
  
About Surface Connections with Triangular Surfaces
Surface connections to triangular surfaces are handled similarly as other connections with the following additional restrictions:
The surface's natural boundary may be a leader or follower of another surface with G1, G2, or G3 connections.
The two edges that are not the natural boundary may be G1 leaders only.