The south wall hoppers are the breathers for the shed. When the air inside is getting to hot these hoppers will let air in from the wet garden that is planned for the south side of the shed.
The other walls will also have their openable doors but this will help guarantee a cross flow of air during that iron roasting summer days.
I still haven't figured out how to make them easy to open and close. Currently I lift one end and prop a piece of offcut timber there. But some sort of pulleys with hinged legs that lock into place would be good.
Aaa another of many chores.