I used to do that. Then bought the slightly more expensive round ones that twist fold up. It's a worthwhile upgrade. They have sizes that fit specific cars better.Yep....keeps the sun from fading and cracking the interior and also reflects the sun. I buy the cheap Walmart ones that are thin and fold up nicely.
Used them and sold them, even the cheap ones are better than nothing !!I have an IntroTech one in each vehicle. I really like them.
The fitted shades, such as those from WeatherTech, fit the window perfectly. Certainly for any car that I have owned. Husky also makes fitted shades and they appear to be even nicer than those from WeatherTech. There are others, I'm sure.I have used, in past, custom cut oldstyle cardboard folding ones. I wish I could still find those old cardboard ones, because they could be made to exact-fit the windshield opening.