To cross a stream, road or valley (where the hold off caused by a flight of locks at possibly facet might be unacceptable) the valley is often spanned by a navigable aqueduct – a popular instance in Wales will be the Pontcysyllte Aqueduct (now a UNESCO Planet Heritage Website) https://canalinfantil83714.blogmazing.com/36139903/helping-the-others-realize-the-advantages-of-urso-fofo