The last one I had in a truck was plastic, and was designed to snap into the window opening by wedging the ends under the rubber gasket as it was installed. It was adjustable for different heights of windows, so it was pretty much of a universal fit item. It held a rifle and a shotgun securely for several years, and stayed with the truck when I sold it. We ran a small herd of beef cattle at the time, and coyotes were a constant problem, especially when newborn calves were around. Having that rifle handy was a really good thing.
Jerry
