After securing the whirly-vent to the flashing, remove some of the foam packers so that you can turn the vent to its optimal angle. The top and bottom of the whirly-vent turn independently. Adjust the two halves of the whirly-vent to change the vent angle. Keep adjusting it until the top of the whirly-vent is sitting flat when you look at it from all angles. If it isn’t, the vent won’t work efficiently. Once the whirly-vent is sitting flat, take the last of the foam packers out, to make sure the vent spins freely.