The picture is one I stole from a thread posted by jpzapata.
I posted it to show something that GM cars are very bad about. I don't know about any others.
In the lower left corner, you can see some sand that has gotten into the crevices of the weatherstrip. This can/will wear through the weatherstrip in time if it isn't removed. In fact, it looks like some damage has already occured on this vehicle. It's an area that is very easy to overlook. I take a plastic spatula and my vacuum cleaner to remove all of it I can. That's usually gets most of it. Medium bristle brush and some APC finishes the job.
Charles
I posted it to show something that GM cars are very bad about. I don't know about any others.
In the lower left corner, you can see some sand that has gotten into the crevices of the weatherstrip. This can/will wear through the weatherstrip in time if it isn't removed. In fact, it looks like some damage has already occured on this vehicle. It's an area that is very easy to overlook. I take a plastic spatula and my vacuum cleaner to remove all of it I can. That's usually gets most of it. Medium bristle brush and some APC finishes the job.

Charles