This is a picture of a vent screened with a screen available at some hardware and roof supply houses. Note that this does not cover the bottom of the vent, only the top. Squirrels can still chew the bottom of the vent, which is a really bad place to have a hole, especially if its on the upside of the vent. You get a water fall into your house if that happens. Critter Quitters cover the entire vent and look great. Homedepot.com and Amazon.