The harbor master notes wind direction by means of flying flags, jotting angles as masts clink and buoys bob on gentle swells.

https://zandervzmg610.rivetgarden.com/posts/from-rags-to-riches-the-financial-value-of-historic-revolutionary-war-flags

The harbor master notes wind route with the aid of flying flags, jotting angles as masts clink and buoys bob on mild swells.