What are these things called?

I knew someone would say that: I'm disappointed that it was you. 

That's interesting, because I did wonder. All of the bridges on the Shroppie  seem to have them, and on other canals which don't have them, there are similar grooves in the stonework. Are they replicas or did they never exist in the first place or what?

Bridge guards?

There are some real ones and I do believe that at some point BW or possibly a canal group of some sort had some cast to put where the original ones were missing. A bit like the milepost situation.

The giveaway is that the cast ones are all identical whereas original ones will be all different.
Take a pic of the next one and see if all the grooves line up.



Eta there are definitely some original ones about otherwise bridges would have got damaged too badly. Similar bits of iron are let into some lock sides where unpowered boats were strapped to stop them.

There are some that were rollers too, near bends.

There is one on the corner near the Anchor inn at Salterforth on the l and l. Sadly that too looks like it's not original and is a bit 'too shiny' like those.

You can normally detect the fake ones because they have a groove ready made for a Shetland Pony.

On the picture mrs tabby posted it does look like there are some rope grooves in the stone work above the guard but not behind it so I think it might be original. Tow ropes were very long so would not necessarily be at a certain height and also there must have been numerous occasions where the "stand by" boat would have slowed down to let another boat through the bridgehole then the horse takes up a slack rope. That could explain the various different heights.

Oh to be a fly on the bridge 150 years ago

It would have been fascinating to see how the problem of passing unpowered (no reverse) boats at a narrow bridge was solved.