The harbor grasp notes wind course by flying flags, jotting angles as masts clink and buoys bob on light swells.

https://blogfreely.net/agnathbmrj/two-flags-one-pole-can-i-fly-two-flags-on-the-same-time

The harbor grasp notes wind path by means of flying flags, jotting angles as masts clink and buoys bob on mild swells.