99 civic ex problem. What is this rubber stopper thing?

I have a: 1999 Honda Civic EX Coupe (2 Door). I'm looking at the doors and above the top part of the window, where the rubber part is, there's a rubber cube like item. What is this? It is about halfway down the rubber. I need to remove this to add a window visor. What is this rubber item and how do I remove it? It is in the picture
Thank you for your help99 civic ex problem. What is this rubber stopper thing

I think it is on there to help guide the window in when rolling the window up while driving and the wind blowing, should not need it anymore with visors, not sure the proper way to get it off, other then get a hold of it with vise grips or something and rip it off. Mine just fell off.

If you roll the window down can you get at it inside the window track? I think its called a doohickey, or a thingamajig. LOL. Really not sure what it is, but it should be removable.