To cross a stream, highway or valley (wherever the delay a result of a flight of locks at possibly aspect will be unacceptable) the valley could be spanned by a navigable aqueduct – a well-known example in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Entire world Heritage https://ursofofo55431.bloggactivo.com/36313948/top-guidelines-of-urso-fofo