The placement of family instances can sometimes be a tricky topic in the Revit API. Programmatically, this is always achieved using the NewFamilyInstance method. However, this method provides 13 different overloads to choose from, which can be a non-trivial task: NewFamilyInstance(Face, Line, FamilySymbol) – Inserts a new instance of a family onto a face of an existing element, using a line on that face for its position, and a type/symbol. NewFamilyInstance(Line, FamilySymbol, View) – Add a line based detail family... Read more →