OK you are talking about hair simu for the hair: you must choose the "main" collision object to attach hair (usually the character) and then you have to select vertices of the scalp of this character to attach the hair (with templates: V4,....). For a standing character and short hair you usually don't need other collision objects But you may need to add other collision objects (sets, clothes,...). For example, in my last render in the "share your VWD render": the hair is attached to the "main object": G3F but I also defined branches and ground as collision objects. Hope I'm clear