Sometimes there's a chance thing that I stumble upon - like today, when I was checking social media, when I found a picture of a curious bridge, with the explanation that this was a special kind of towpath bridge. The design allowed the horse to change sides without unhitching the towline.
The bridge looks really beautiful:
It's on the Macclesfield Canal in Britain. If you'd like to read more about roving bridges, there's a Wikipedia article about it, and there's a few more images of the bridge, towing horses, and general information about boat towing here at exploringgb.co.uk.