If you look at the wall of your home, you are likely to find air conditioning (AC) vents. They are the means that cooled air flows into your home from your HVAC system. These vents also serve to provide heat in the winter. If you find your room remaining too cool in the summer or too hot in the winter, you may want to blank off one of the AC vents. Installing a temporary blank-off will prevent air from flowing in the room, but since it is not a permanent change you can always revert back to the original system by removing the blank-off.
Clean the front of the AC vent. Wipe all the dust and debris from it and then wash with warm and soapy water. The cover will adhere much better to a clean vent.
Align one corner of the magnetic blank-off with one corner of the AC vent. Allow the corner to magnetically adhere to the AC vent.
Push the magnetic blank-off against the AC vent. Go slow to ensure the blank-off is installed so that the edges match up with the edges of the AC vent.
Smooth out the blank-off with your fingers and remove any air bubbles that might have formed under the blank-off.
Covering more than a few of your AC vents at a given time may add stress to your HVAC system. Covering vents increases static pressure in your duct work and if it gets too high, it will shorten the life of the system.