To cross a stream, highway or valley (wherever the hold off attributable to a flight of locks at either side could well be unacceptable) the valley is usually spanned by a navigable aqueduct – a well known illustration in Wales may be the Pontcysyllte Aqueduct (now a UNESCO Globe https://canalinfantil33210.win-blog.com/17931783/not-known-details-about-urso-fofo