Eli5 how brick bridges are built.

Question

I’ve been watching a narrowboat channel from England and there are very many beautiful brick bridges with a nice arch over the canal. I understand how the arch holds the bridge up.

I don’t understand how they built the arch in the first place without the bricks falling. They were built a couple hundred years ago.

In: 73

Answer 1

Wood frames are built to lay the initial stones on, until the key stone can be set in place. Once the key stone is in place, the arch is self supporting.