TrigpointingUK

Hey does anyone know why Topographs were built? Can’t see anything on the wiki.

In my experience, the main purpose of a topograph is to tell you
what you might have seen from a hill top had it not been raining

Topographs are rarely used as trigpoints, but a few examples are described at:
https://trigpointing.uk/w/index.php?title=Topograph

Thanks again Ted for another reply
In my short experience, I have visited one (Hindhead) but I thought it was just a little extra. Now I know!