[Mikendebbie]

This is a pic looking up inside of my vent outlet. There are two movable tabs inside that hold the flap - unfortunately the pic is a bit too dark to see them clearly - so I outliined them in gray. When the tabs are horizontal - the vent door is held shut. When you turn the tabs down or up (vertical - I outlined in red) the door flap is open and will let the venthood air flow out.