To cross a stream, street or valley (where by the hold off due to a flight of locks at both side would be unacceptable) the valley can be spanned by a navigable aqueduct – a famed illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Planet Heritage https://canal-infantil68887.blog-gold.com/49378640/musica-infantil-can-be-fun-for-anyone