I appreciate the comments on this post, because my sister-in-law asked about such a device last week and I told her I didn't think there was much value. Now that I've thought of it more, I think that it might be a good tool to have in your auto, for someone else's sake. Since coming to this site some time ago, I always carry my benchmade mini-griptillian, so the knife is covered. But I remember following a car back from skiing and the driver fell asleep and rolled over, landing on it's top. The doors wouldn't open, but they weren't hurt bad enough to not roll the window down. Suppose they were and you needed to get them out? Another time, a car was pinned against a railing, next to the river, by a semi that lost it's traction. The only way out was through the hatch. What if it didn't have a hatch? Sure you can use other devices, but for $10, it could be handy. I also wonder if it might have a use for travelling and might be effective on 3/8in hotel room glass? Just thinking out loud.