Several years ago, a cousin gave each of our sons a WWI bayonet that had belonged to his uncle. We also have two pictures of him; this one was taken in 1923.
I’m not sure when B started using one of the bayonets to open and close the ceiling vents in the guest room and the office. The little levers can be stubborn, and the steel bayonet is just the ticket for the stretch and the push needed to operate the vent.
We keep the vents closed when the rooms are not being used.
This is one way we have found to take a stab at cutting our utility bills.