The definition of the northern boundary of the state is unusual. Consider a zone with an irrigation canal defining one boundary. Collectively they extended beyond the current Chesham town boundary. Thus ambiguity over the water boundary remained. The urbanization on both sides of the provincial boundary is identical. Euroregions are similar official structures built around commuting across boundary. Twinning is a phenomenon somewhere between a crystallographic defect and a grain boundary. This makes the upper boundary of the trigone. Ownership of a fence on a boundary varies. The Thames forms part of the county's southwestern boundary. They disagreed, however, over the definition of the eastern boundary. The fault runs along an ancient Precambrian terrane boundary. Point Roberts is a U.S. exclave bordered by Canada and the waters of Boundary Bay. The Blackfeet Indian Reservation provides most of the eastern boundary. This is the northern boundary of Judea.