They are sort of a tight press fit, push it into the door frame and start all screws but don't tighten until they are all made. The making can require some pushing and prying, I bought a cheap set of nylon trim paddles from Harbor Frieght, they are good and don't mark up the surfaces. It does fit tight against the window channel and you want to install it with the window rolled down. It will seem like it won't fit but it will with some gentle persuasion here and there. Good Luck!
