To cross a stream, road or valley (where the hold off because of a flight of locks at either facet could well be unacceptable) the valley is usually spanned by a navigable aqueduct – a well known illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Earth https://canalinfantil99593.digiblogbox.com/61570304/considerations-to-know-about-urso-fofo