To cross a stream, street or valley (where by the hold off caused by a flight of locks at either aspect can be unacceptable) the valley is usually spanned by a navigable aqueduct – a famous example in Wales is the Pontcysyllte Aqueduct (now a UNESCO Environment Heritage Website) https://canal-infantil11008.dm-blog.com/37139306/5-easy-facts-about-musica-infantil-described