To cross a stream, road or valley (wherever the hold off because of a flight of locks at possibly side will be unacceptable) the valley is often spanned by a navigable aqueduct – a famed case in point in Wales could be the Pontcysyllte Aqueduct (now a UNESCO Environment https://musica-infantil00099.bloggerswise.com/44913385/how-much-you-need-to-expect-you-ll-pay-for-a-good-musica-infantil