If you have to remove the glass, there are 2 screws in the rubber at the top of the vent frame. Remove them and twead the rail out. You may have to remove the bump stop, but other than that roll up the window, or down real low and wiggle it out of the plastic roller channel. Be careful not to screw up the sleve that rides inside the rail and keeps your window from rattling. If you remove the lower stop, you may get the window low enough to change the catwiskers with the window in place. It's been a year or 2 since I did it. It is faily simple.