To cross a stream, road or valley (exactly where the hold off because of a flight of locks at possibly aspect will be unacceptable) the valley could be spanned by a navigable aqueduct – a well-known case in point in Wales could be the Pontcysyllte Aqueduct (now a UNESCO https://urso-fofo45431.blogscribble.com/37284765/new-step-by-step-map-for-urso-fofo