11.   Pushing the straw upright again closes the vent, supposedly allowing people who like to drive and drink coffee to brace the cup safely with their legs.

12.   Roll up the car windows, shut off the air conditioner, close the vents and breathe into a shirt sleeve or other clothing.

13.   The covers on the vents are strange, but they may hark back to a time when it was thought OK to close the vents in winter.

14.   The only way to control the flow of heated or cooled air from the automatic climate control system is by manually opening and closing the vents.

15.   The vents are closed for the winter, but the water gets around the cover and drips right out.

16.   Then cover the grill, close the vents and let it get really hot inside, like heating an oven.

17.   The vents were closed because dehumidifiers have to work in still air.

18.   There is no provision for closing those vents.

19.   Turn thermostats off and close the vents in unoccupied rooms.

20.   Winter ventilation is not necessary, so you can close the vents to keep the crawl space from getting colder than necessary.